diff --git a/src/stan/mcmc/hmc/base_hmc.hpp b/src/stan/mcmc/hmc/base_hmc.hpp
index d170ff4f6b..80c26f7595 100644
--- a/src/stan/mcmc/hmc/base_hmc.hpp
+++ b/src/stan/mcmc/hmc/base_hmc.hpp
@@ -70,6 +70,7 @@ class base_hmc : public base_mcmc {
   void write_sampler_state_struct(callbacks::structured_writer& struct_writer) {
     struct_writer.begin_record();
     struct_writer.write("stepsize", get_nominal_stepsize());
+    struct_writer.write("metric_type", z_.metric_type());
     struct_writer.write("inv_metric", z_.inv_e_metric_);
     struct_writer.end_record();
   }
diff --git a/src/stan/mcmc/hmc/hamiltonians/dense_e_point.hpp b/src/stan/mcmc/hmc/hamiltonians/dense_e_point.hpp
index 3b811e280e..ac5b4c3eaf 100644
--- a/src/stan/mcmc/hmc/hamiltonians/dense_e_point.hpp
+++ b/src/stan/mcmc/hmc/hamiltonians/dense_e_point.hpp
@@ -51,6 +51,8 @@ class dense_e_point : public ps_point {
       writer(inv_e_metric_ss.str());
     }
   }
+
+  inline std::string metric_type() { return "dense_e"; }
 };
 
 }  // namespace mcmc
diff --git a/src/stan/mcmc/hmc/hamiltonians/diag_e_point.hpp b/src/stan/mcmc/hmc/hamiltonians/diag_e_point.hpp
index eb2c2d9f5d..f5a15de2cb 100644
--- a/src/stan/mcmc/hmc/hamiltonians/diag_e_point.hpp
+++ b/src/stan/mcmc/hmc/hamiltonians/diag_e_point.hpp
@@ -49,6 +49,8 @@ class diag_e_point : public ps_point {
       inv_e_metric_ss << ", " << inv_e_metric_(i);
     writer(inv_e_metric_ss.str());
   }
+
+  inline std::string metric_type() { return "diag_e"; }
 };
 
 }  // namespace mcmc
diff --git a/src/stan/mcmc/hmc/hamiltonians/softabs_point.hpp b/src/stan/mcmc/hmc/hamiltonians/softabs_point.hpp
index bddd225f9f..b782e2a09c 100644
--- a/src/stan/mcmc/hmc/hamiltonians/softabs_point.hpp
+++ b/src/stan/mcmc/hmc/hamiltonians/softabs_point.hpp
@@ -43,6 +43,8 @@ class softabs_point : public ps_point {
   virtual inline void write_metric(stan::callbacks::writer& writer) {
     writer("No free parameters for SoftAbs metric");
   }
+
+  inline std::string metric_type() { return "softabs"; }
 };
 
 }  // namespace mcmc
diff --git a/src/stan/mcmc/hmc/hamiltonians/unit_e_point.hpp b/src/stan/mcmc/hmc/hamiltonians/unit_e_point.hpp
index cb6b439409..c4e9933464 100644
--- a/src/stan/mcmc/hmc/hamiltonians/unit_e_point.hpp
+++ b/src/stan/mcmc/hmc/hamiltonians/unit_e_point.hpp
@@ -30,6 +30,8 @@ class unit_e_point : public ps_point {
   inline void write_metric(stan::callbacks::writer& writer) {
     writer("No free parameters for unit metric");
   }
+
+  inline std::string metric_type() { return "unit_e"; }
 };
 
 }  // namespace mcmc
diff --git a/src/test/unit/services/sample/hmc_nuts_dense_e_adapt_parallel_match_test.cpp b/src/test/unit/services/sample/hmc_nuts_dense_e_adapt_parallel_match_test.cpp
index 1250f05dc9..f98c59a820 100644
--- a/src/test/unit/services/sample/hmc_nuts_dense_e_adapt_parallel_match_test.cpp
+++ b/src/test/unit/services/sample/hmc_nuts_dense_e_adapt_parallel_match_test.cpp
@@ -125,6 +125,7 @@ TEST_F(ServicesSampleHmcNutsDenseEAdaptParMatch, single_multi_match) {
     par_metrics.push_back(ss_metric[i].str());
     ASSERT_TRUE(stan::test::is_valid_JSON(par_metrics[i]));
     EXPECT_EQ(count_matches("stepsize", par_metrics[i]), 1);
+    EXPECT_EQ(count_matches("metric_type", par_metrics[i]), 1);
     EXPECT_EQ(count_matches("inv_metric", par_metrics[i]), 1);
     EXPECT_EQ(count_matches("[", par_metrics[i]), 3);  // list has 2 rows
   }
diff --git a/src/test/unit/services/sample/hmc_nuts_diag_e_adapt_parallel_match_test.cpp b/src/test/unit/services/sample/hmc_nuts_diag_e_adapt_parallel_match_test.cpp
index 50da61b09f..ca3b326c54 100644
--- a/src/test/unit/services/sample/hmc_nuts_diag_e_adapt_parallel_match_test.cpp
+++ b/src/test/unit/services/sample/hmc_nuts_diag_e_adapt_parallel_match_test.cpp
@@ -124,6 +124,7 @@ TEST_F(ServicesSampleHmcNutsDiagEAdaptParMatch, single_multi_match) {
     par_metrics.push_back(ss_metric[i].str());
     ASSERT_TRUE(stan::test::is_valid_JSON(par_metrics[i]));
     EXPECT_EQ(count_matches("stepsize", par_metrics[i]), 1);
+    EXPECT_EQ(count_matches("metric_type", par_metrics[i]), 1);
     EXPECT_EQ(count_matches("inv_metric", par_metrics[i]), 1);
     EXPECT_EQ(count_matches("[", par_metrics[i]), 1);  // single list
   }
diff --git a/src/test/unit/services/sample/hmc_nuts_unit_e_adapt_parallel_test.cpp b/src/test/unit/services/sample/hmc_nuts_unit_e_adapt_parallel_test.cpp
index 5574fa685a..2889c6b229 100644
--- a/src/test/unit/services/sample/hmc_nuts_unit_e_adapt_parallel_test.cpp
+++ b/src/test/unit/services/sample/hmc_nuts_unit_e_adapt_parallel_test.cpp
@@ -128,6 +128,7 @@ TEST_F(ServicesSampleHmcNutsUnitEAdaptPar, parameter_checks) {
     // Adapted metric
     ASSERT_TRUE(stan::test::is_valid_JSON(metric));
     EXPECT_EQ(count_matches("stepsize", metric), 1);
+    EXPECT_EQ(count_matches("metric_type", metric), 1);
     EXPECT_EQ(count_matches("inv_metric", metric), 1);
     EXPECT_EQ(count_matches("[", metric), 1);         // single list
     EXPECT_EQ(count_matches("[ 1, 1 ]", metric), 1);  // unit diagonal