diff --git a/dvc/repo/index.py b/dvc/repo/index.py
index 18eb6d2a98..cd52979285 100644
--- a/dvc/repo/index.py
+++ b/dvc/repo/index.py
@@ -68,14 +68,50 @@ def __init__(
         if stages is not None:
             self.stages: List["Stage"] = stages
         self._collected_targets: Dict[int, List["StageInfo"]] = {}
+        self._metrics: Dict[str, List[str]] = {}
+        self._plots: Dict[str, Any] = {}
+        self._params: Dict[str, List[str]] = {}
 
     @cached_property
     def stages(self) -> List["Stage"]:  # pylint: disable=method-hidden
         # note that ideally we should be keeping this in a set as it is unique,
         # hashable and has no concept of orderliness on its own. But we depend
         # on this to be somewhat ordered for status/metrics/plots, etc.
+        return self._collect()
+
+    @cached_property
+    def _top_metrics(self):
+        self._collect()
+        return self._metrics
+
+    @cached_property
+    def _top_plots(self):
+        self._collect()
+        return self._plots
+
+    @cached_property
+    def _top_params(self):
+        self._collect()
+        return self._params
+
+    def _collect(self):
+        if "stages" in self.__dict__:
+            return self.stages
+
         onerror = self.repo.stage_collection_error_handler
-        return self.stage_collector.collect_repo(onerror=onerror)
+
+        # pylint: disable=protected-access
+        (
+            stages,
+            metrics,
+            plots,
+            params,
+        ) = self.stage_collector._collect_all_from_repo(onerror=onerror)
+        self.stages = stages
+        self._metrics = metrics
+        self._plots = plots
+        self._params = params
+        return stages
 
     def __repr__(self) -> str:
         from dvc.fs import LocalFileSystem
diff --git a/dvc/repo/metrics/show.py b/dvc/repo/metrics/show.py
index 69dc7c1ae0..82ca5cfa4c 100644
--- a/dvc/repo/metrics/show.py
+++ b/dvc/repo/metrics/show.py
@@ -9,7 +9,12 @@
 from dvc.repo import locked
 from dvc.repo.collect import StrPaths, collect
 from dvc.scm import NoSCMError
-from dvc.utils import error_handler, errored_revisions, onerror_collect
+from dvc.utils import (
+    as_posix,
+    error_handler,
+    errored_revisions,
+    onerror_collect,
+)
 from dvc.utils.collections import ensure_list
 from dvc.utils.serialize import load_path
 
@@ -28,6 +33,17 @@ def _to_fs_paths(metrics: List[Output]) -> StrPaths:
     return result
 
 
+def _collect_top_level_metrics(repo):
+    top_metrics = repo.index._top_metrics  # pylint: disable=protected-access
+    for dvcfile, metrics in top_metrics.items():
+        wdir = repo.fs.path.relpath(
+            repo.fs.path.parent(dvcfile), repo.root_dir
+        )
+        for file in metrics:
+            path = repo.fs.path.join(wdir, as_posix(file))
+            yield repo.fs.path.normpath(path)
+
+
 def _collect_metrics(repo, targets, revision, recursive):
     metrics, fs_paths = collect(
         repo,
@@ -94,6 +110,7 @@ def _read_metrics(repo, metrics, rev, onerror=None):
 
 def _gather_metrics(repo, targets, rev, recursive, onerror=None):
     metrics = _collect_metrics(repo, targets, rev, recursive)
+    metrics.extend(_collect_top_level_metrics(repo))
     return _read_metrics(repo, metrics, rev, onerror=onerror)
 
 
diff --git a/dvc/repo/params/show.py b/dvc/repo/params/show.py
index 684eb4037d..f4a9b48c32 100644
--- a/dvc/repo/params/show.py
+++ b/dvc/repo/params/show.py
@@ -20,7 +20,12 @@
 from dvc.scm import NoSCMError
 from dvc.stage import PipelineStage
 from dvc.ui import ui
-from dvc.utils import error_handler, errored_revisions, onerror_collect
+from dvc.utils import (
+    as_posix,
+    error_handler,
+    errored_revisions,
+    onerror_collect,
+)
 from dvc.utils.collections import ensure_list
 from dvc.utils.serialize import load_path
 
@@ -35,6 +40,17 @@ def _is_params(dep: "Output"):
     return isinstance(dep, ParamsDependency)
 
 
+def _collect_top_level_params(repo):
+    top_params = repo.index._top_params  # pylint: disable=protected-access
+    for dvcfile, params in top_params.items():
+        wdir = repo.fs.path.relpath(
+            repo.fs.path.parent(dvcfile), repo.root_dir
+        )
+        for file in params:
+            path = repo.fs.path.join(wdir, as_posix(file))
+            yield repo.fs.path.normpath(path)
+
+
 def _collect_configs(
     repo: "Repo", rev, targets=None, deps=False, stages=None
 ) -> Tuple[List["Output"], List[str]]:
@@ -176,6 +192,7 @@ def _gather_params(
     param_outs, params_fs_paths = _collect_configs(
         repo, rev, targets=targets, deps=deps, stages=stages
     )
+    params_fs_paths.extend(_collect_top_level_params(repo=repo))
     params = _read_params(
         repo,
         params=param_outs,
diff --git a/dvc/repo/plots/__init__.py b/dvc/repo/plots/__init__.py
index 755980ddd2..74f12a4f4a 100644
--- a/dvc/repo/plots/__init__.py
+++ b/dvc/repo/plots/__init__.py
@@ -439,36 +439,33 @@ def _resolve_definitions(
 
 
 def _collect_pipeline_files(repo, targets: List[str], props, onerror=None):
-    from dvc.dvcfile import PipelineFile
-
     result: Dict[str, Dict] = {}
-    dvcfiles = {stage.dvcfile for stage in repo.index.stages}
-    for dvcfile in dvcfiles:
-        if isinstance(dvcfile, PipelineFile):
-            dvcfile_path = _relpath(repo.dvcfs, dvcfile.path)
-            dvcfile_defs = dvcfile.load().get("plots", {})
-            dvcfile_defs_dict: Dict[str, Union[Dict, None]] = {}
-            if isinstance(dvcfile_defs, list):
-                for elem in dvcfile_defs:
-                    if isinstance(elem, str):
-                        dvcfile_defs_dict[elem] = None
-                    else:
-                        k, v = list(elem.items())[0]
-                        dvcfile_defs_dict[k] = v
-            else:
-                dvcfile_defs_dict = dvcfile_defs
-            resolved = _resolve_definitions(
-                repo.dvcfs,
-                targets,
-                props,
-                dvcfile_path,
-                dvcfile_defs_dict,
-                onerror=onerror,
-            )
-            dpath.util.merge(
-                result,
-                {dvcfile_path: resolved},
-            )
+    top_plots = repo.index._top_plots  # pylint: disable=protected-access
+    for dvcfile, plots_def in top_plots.items():
+        dvcfile_path = _relpath(repo.dvcfs, dvcfile)
+        dvcfile_defs_dict: Dict[str, Union[Dict, None]] = {}
+        if isinstance(plots_def, list):
+            for elem in plots_def:
+                if isinstance(elem, str):
+                    dvcfile_defs_dict[elem] = None
+                else:
+                    k, v = list(elem.items())[0]
+                    dvcfile_defs_dict[k] = v
+        else:
+            dvcfile_defs_dict = plots_def
+
+        resolved = _resolve_definitions(
+            repo.dvcfs,
+            targets,
+            props,
+            dvcfile_path,
+            dvcfile_defs_dict,
+            onerror=onerror,
+        )
+        dpath.util.merge(
+            result,
+            {dvcfile_path: resolved},
+        )
     return result
 
 
diff --git a/dvc/repo/stage.py b/dvc/repo/stage.py
index 84b4629fef..14a33786d5 100644
--- a/dvc/repo/stage.py
+++ b/dvc/repo/stage.py
@@ -502,3 +502,104 @@ def is_out_or_ignored(root, directory):
 
     def collect_repo(self, onerror: Callable[[str, Exception], None] = None):
         return list(self._collect_repo(onerror))
+
+    def _load_file(self, path):
+        from dvc.dvcfile import Dvcfile
+        from dvc.stage.loader import SingleStageLoader, StageLoader
+
+        path = self._get_filepath(path)
+        dvcfile = Dvcfile(self.repo, path)
+        # `dvcfile.stages` is not cached
+        stages = dvcfile.stages  # type: ignore
+
+        if isinstance(stages, SingleStageLoader):
+            stages_ = [stages[None]]
+        else:
+            assert isinstance(stages, StageLoader)
+            keys = self._get_keys(stages)
+            stages_ = [stages[key] for key in keys]
+
+        return (
+            stages_,
+            stages.metrics_data,
+            stages.plots_data,
+            stages.params_data,
+        )
+
+    def _collect_all_from_repo(
+        self, onerror: Callable[[str, Exception], None] = None
+    ):
+        """Collects all of the stages present in the DVC repo.
+
+        Args:
+            onerror (optional): callable that will be called with two args:
+                the filepath whose collection failed and the exc instance.
+                It can report the error to continue with the collection
+                (and, skip failed ones), or raise the exception to abort
+                the collection.
+        """
+        from dvc.dvcfile import is_valid_filename
+        from dvc.fs import LocalFileSystem
+
+        scm = self.repo.scm
+        sep = self.fs.sep
+        outs: Set[str] = set()
+
+        is_local_fs = isinstance(self.fs, LocalFileSystem)
+
+        def is_ignored(path):
+            # apply only for the local fs
+            return is_local_fs and scm.is_ignored(path)
+
+        def is_dvcfile_and_not_ignored(root, file):
+            return is_valid_filename(file) and not is_ignored(
+                f"{root}{sep}{file}"
+            )
+
+        def is_out_or_ignored(root, directory):
+            dir_path = f"{root}{sep}{directory}"
+            # trailing slash needed to check if a directory is gitignored
+            return dir_path in outs or is_ignored(f"{dir_path}{sep}")
+
+        walk_iter = self.repo.dvcignore.walk(self.fs, self.repo.root_dir)
+        if logger.isEnabledFor(logging.TRACE):  # type: ignore[attr-defined]
+            walk_iter = log_walk(walk_iter)
+
+        stages = []
+        metrics = {}
+        plots = {}
+        params = {}
+
+        for root, dirs, files in walk_iter:
+            dvcfile_filter = partial(is_dvcfile_and_not_ignored, root)
+            for file in filter(dvcfile_filter, files):
+                file_path = self.fs.path.join(root, file)
+                try:
+                    (
+                        new_stages,
+                        new_metrics,
+                        new_plots,
+                        new_params,
+                    ) = self._load_file(file_path)
+                except DvcException as exc:
+                    if onerror:
+                        onerror(relpath(file_path), exc)
+                        continue
+                    raise
+
+                stages.extend(new_stages)
+                if new_metrics:
+                    metrics[file_path] = new_metrics
+                if new_plots:
+                    plots[file_path] = new_plots
+                if new_params:
+                    params[file_path] = new_params
+
+                outs.update(
+                    out.fspath
+                    for stage in new_stages
+                    for out in stage.outs
+                    if out.protocol == "local"
+                )
+            dirs[:] = [d for d in dirs if not is_out_or_ignored(root, d)]
+        return stages, metrics, plots, params
diff --git a/dvc/schema.py b/dvc/schema.py
index b48f61aa09..02c16c2760 100644
--- a/dvc/schema.py
+++ b/dvc/schema.py
@@ -123,6 +123,8 @@ def validator(data):
     PLOTS: Any(SINGLE_PLOT_SCHEMA, [Any(str, SINGLE_PLOT_SCHEMA)]),
     STAGES: SINGLE_PIPELINE_STAGE_SCHEMA,
     VARS_KWD: VARS_SCHEMA,
+    StageParams.PARAM_PARAMS: [str],
+    StageParams.PARAM_METRICS: [str],
 }
 
 COMPILED_SINGLE_STAGE_SCHEMA = Schema(SINGLE_STAGE_SCHEMA)
diff --git a/dvc/stage/loader.py b/dvc/stage/loader.py
index 391e43f38f..93092e3894 100644
--- a/dvc/stage/loader.py
+++ b/dvc/stage/loader.py
@@ -24,6 +24,9 @@ def __init__(self, dvcfile, data, lockfile_data=None):
         self.dvcfile = dvcfile
         self.data = data or {}
         self.stages_data = self.data.get("stages", {})
+        self.metrics_data = self.data.get("metrics", [])
+        self.params_data = self.data.get("params", [])
+        self.plots_data = self.data.get("plots", {})
         self.repo = self.dvcfile.repo
 
         lockfile_data = lockfile_data or {}
@@ -171,6 +174,9 @@ def __init__(self, dvcfile, stage_data, stage_text=None):
         self.dvcfile = dvcfile
         self.stage_data = stage_data or {}
         self.stage_text = stage_text
+        self.metrics_data = []
+        self.params_data = []
+        self.plots_data = {}
 
     def __getitem__(self, item):
         if item:
diff --git a/tests/func/metrics/test_diff.py b/tests/func/metrics/test_diff.py
index c88085d31a..23adde515c 100644
--- a/tests/func/metrics/test_diff.py
+++ b/tests/func/metrics/test_diff.py
@@ -1,6 +1,10 @@
 import json
+from os.path import join
+
+import pytest
 
 from dvc.cli import main
+from dvc.utils import relpath
 
 
 def test_metrics_diff_simple(tmp_dir, scm, dvc, run_copy_metrics):
@@ -206,3 +210,28 @@ def _gen(val):
     assert result == {
         "some_file.yaml": {"foo": {"old": 1, "new": 3, "diff": 2}}
     }
+
+
+@pytest.mark.parametrize(
+    "dvcfile, metrics_file",
+    [
+        ("dvc.yaml", "my_metrics.yaml"),
+        ("dir/dvc.yaml", "my_metrics.yaml"),
+        ("dir/dvc.yaml", join("..", "my_metrics.yaml")),
+    ],
+)
+def test_diff_top_level_metrics(tmp_dir, dvc, scm, dvcfile, metrics_file):
+    directory = (tmp_dir / dvcfile).parent
+    directory.mkdir(exist_ok=True)
+    (tmp_dir / dvcfile).dump({"metrics": [metrics_file]})
+
+    metrics_file = directory / metrics_file
+    metrics_file.dump({"foo": 3})
+    scm.add_commit([metrics_file, tmp_dir / dvcfile], message="add metrics")
+
+    metrics_file.dump({"foo": 5})
+    assert dvc.metrics.diff() == {
+        relpath(directory / metrics_file): {
+            "foo": {"diff": 2, "new": 5, "old": 3}
+        }
+    }
diff --git a/tests/func/params/test_diff.py b/tests/func/params/test_diff.py
index f409e40124..ba181ba38b 100644
--- a/tests/func/params/test_diff.py
+++ b/tests/func/params/test_diff.py
@@ -1,3 +1,5 @@
+from os.path import join
+
 import pytest
 
 from dvc.utils import relpath
@@ -241,3 +243,28 @@ def test_diff_without_targets_specified(tmp_dir, dvc, scm, file):
             "y": {"new": "100", "old": None},
         }
     }
+
+
+@pytest.mark.parametrize(
+    "dvcfile, params_file",
+    [
+        ("dvc.yaml", "my_params.yaml"),
+        ("dir/dvc.yaml", "my_params.yaml"),
+        ("dir/dvc.yaml", join("..", "my_params.yaml")),
+    ],
+)
+def test_diff_top_level_params(tmp_dir, dvc, scm, dvcfile, params_file):
+    directory = (tmp_dir / dvcfile).parent
+    directory.mkdir(exist_ok=True)
+    (tmp_dir / dvcfile).dump({"params": [params_file]})
+
+    params_file = directory / params_file
+    params_file.dump({"foo": 3})
+    scm.add_commit([params_file, tmp_dir / dvcfile], message="add params")
+
+    params_file.dump({"foo": 5})
+    assert dvc.params.diff() == {
+        relpath(directory / params_file): {
+            "foo": {"diff": 2, "new": 5, "old": 3}
+        }
+    }
diff --git a/tests/unit/command/test_status.py b/tests/unit/command/test_status.py
index 301982f0f1..fd69a84f59 100644
--- a/tests/unit/command/test_status.py
+++ b/tests/unit/command/test_status.py
@@ -81,7 +81,7 @@ def test_status_empty(dvc, mocker, capsys):
 
     cmd = cli_args.func(cli_args)
 
-    spy = mocker.spy(cmd.repo.stage, "_collect_repo")
+    spy = mocker.spy(cmd.repo.stage, "_collect_all_from_repo")
 
     assert cmd.run() == 0
 
@@ -108,7 +108,10 @@ def test_status_up_to_date(dvc, mocker, capsys, cloud_opts, expected_message):
     mocker.patch.dict(cmd.repo.config, {"core": {"remote": "default"}})
     mocker.patch.object(cmd.repo, "status", autospec=True, return_value={})
     mocker.patch.object(
-        cmd.repo.stage, "_collect_repo", return_value=[object()], autospec=True
+        cmd.repo.stage,
+        "_collect_all_from_repo",
+        return_value=[[object()], {}, {}, {}],
+        autospec=True,
     )
 
     assert cmd.run() == 0