diff --git a/dvc/command/metrics.py b/dvc/command/metrics.py
index 3c22a0321..9daf5984a 100644
--- a/dvc/command/metrics.py
+++ b/dvc/command/metrics.py
@@ -76,7 +76,7 @@ class CmdMetricsShow(CmdMetricsBase):
         return 0
 
 
-def _show_diff(diff, markdown=False, no_path=False, old=False, precision=None):
+def _show_diff(diff, markdown=False, no_path=False, precision=None):
     from collections import OrderedDict
 
     from dvc.utils.diff import table
@@ -96,18 +96,14 @@ def _show_diff(diff, markdown=False, no_path=False, old=False, precision=None):
         for metric, change in sorted_mdiff.items():
             row = [] if no_path else [fname]
             row.append(metric)
-            if old:
-                row.append(_round(change.get("old")))
+            row.append(_round(change.get("old")))
             row.append(_round(change["new"]))
-            row.append(_round(change.get("diff", "diff not supported")))
+            row.append(_round(change.get("diff")))
             rows.append(row)
 
     header = [] if no_path else ["Path"]
     header.append("Metric")
-    if old:
-        header.extend(["Old", "New"])
-    else:
-        header.append("Value")
+    header.extend(["Old", "New"])
     header.append("Change")
 
     return table(header, rows, markdown)
@@ -133,7 +129,6 @@ class CmdMetricsDiff(CmdMetricsBase):
                     diff,
                     self.args.show_md,
                     self.args.no_path,
-                    self.args.old,
                     precision=self.args.precision,
                 )
                 if table:
@@ -275,12 +270,6 @@ def add_parser(subparsers, parent_parser):
         default=False,
         help="Show tabulated output in the Markdown format (GFM).",
     )
-    metrics_diff_parser.add_argument(
-        "--old",
-        action="store_true",
-        default=False,
-        help="Show old metric value.",
-    )
     metrics_diff_parser.add_argument(
         "--no-path",
         action="store_true",
diff --git a/dvc/utils/diff.py b/dvc/utils/diff.py
index 219691359..d12267f64 100644
--- a/dvc/utils/diff.py
+++ b/dvc/utils/diff.py
@@ -97,7 +97,7 @@ def table(header, rows, markdown=False):
         tablefmt="github" if markdown else "plain",
         disable_numparse=True,
         # None will be shown as "" by default, overriding
-        missingval="None",
+        missingval="—",
     )
 
     if markdown:
diff --git a/tests/func/metrics/test_diff.py b/tests/func/metrics/test_diff.py
index 8d00c2d81..94b4cc255 100644
--- a/tests/func/metrics/test_diff.py
+++ b/tests/func/metrics/test_diff.py
@@ -185,7 +185,7 @@ def test_metrics_diff_cli(tmp_dir, scm, dvc, run_copy_metrics, caplog, capsys):
     _gen(3.45678910111213)
 
     caplog.clear()
-    assert main(["metrics", "diff", "HEAD~2", "--old"]) == 0
+    assert main(["metrics", "diff", "HEAD~2"]) == 0
     (info,) = [
         msg
         for name, level, msg in caplog.record_tuples
diff --git a/tests/unit/command/test_metrics.py b/tests/unit/command/test_metrics.py
index 1e8650556..aede55a30 100644
--- a/tests/unit/command/test_metrics.py
+++ b/tests/unit/command/test_metrics.py
@@ -24,7 +24,6 @@ def test_metrics_diff(dvc, mocker):
             "target2",
             "--show-md",
             "--no-path",
-            "--old",
             "--precision",
             "10",
         ]
@@ -51,8 +50,8 @@ def test_metrics_show_json_diff():
         {"metrics.json": {"a.b.c": {"old": 1, "new": 2, "diff": 3}}}
     ) == textwrap.dedent(
         """\
-        Path          Metric    Value    Change
-        metrics.json  a.b.c     2        3"""
+        Path          Metric    Old    New    Change
+        metrics.json  a.b.c     1      2      3"""
     )
 
 
@@ -61,8 +60,8 @@ def test_metrics_show_raw_diff():
         {"metrics": {"": {"old": "1", "new": "2"}}}
     ) == textwrap.dedent(
         """\
-        Path     Metric    Value    Change
-        metrics            2        diff not supported"""
+        Path     Metric    Old    New    Change
+        metrics            1      2      —"""
     )
 
 
@@ -71,8 +70,8 @@ def test_metrics_diff_no_diff():
         {"other.json": {"a.b.d": {"old": "old", "new": "new"}}}
     ) == textwrap.dedent(
         """\
-        Path        Metric    Value    Change
-        other.json  a.b.d     new      diff not supported"""
+        Path        Metric    Old    New    Change
+        other.json  a.b.d     old    new    —"""
     )
 
 
@@ -85,8 +84,8 @@ def test_metrics_diff_new_metric():
         {"other.json": {"a.b.d": {"old": None, "new": "new"}}}
     ) == textwrap.dedent(
         """\
-        Path        Metric    Value    Change
-        other.json  a.b.d     new      diff not supported"""
+        Path        Metric    Old    New    Change
+        other.json  a.b.d     —      new    —"""
     )
 
 
@@ -95,8 +94,8 @@ def test_metrics_diff_deleted_metric():
         {"other.json": {"a.b.d": {"old": "old", "new": None}}}
     ) == textwrap.dedent(
         """\
-        Path        Metric    Value    Change
-        other.json  a.b.d     None     diff not supported"""
+        Path        Metric    Old    New    Change
+        other.json  a.b.d     old    —      —"""
     )
 
 
@@ -143,14 +142,14 @@ def test_metrics_diff_precision():
 
     assert _show_diff(diff) == textwrap.dedent(
         """\
-        Path        Metric    Value    Change
-        other.json  a.b       0.76543  0.64198"""
+        Path        Metric    Old      New      Change
+        other.json  a.b       0.12346  0.76543  0.64198"""
     )
 
     assert _show_diff(diff, precision=10) == textwrap.dedent(
         """\
-        Path        Metric    Value         Change
-        other.json  a.b       0.7654321012  0.6419754012"""
+        Path        Metric    Old        New           Change
+        other.json  a.b       0.1234567  0.7654321012  0.6419754012"""
     )
 
 
@@ -165,18 +164,18 @@ def test_metrics_diff_sorted():
         }
     ) == textwrap.dedent(
         """\
-        Path          Metric    Value    Change
-        metrics.yaml  a.b.c     2        1
-        metrics.yaml  a.d.e     4        1
-        metrics.yaml  x.b       6        1"""
+        Path          Metric    Old    New    Change
+        metrics.yaml  a.b.c     1      2      1
+        metrics.yaml  a.d.e     3      4      1
+        metrics.yaml  x.b       5      6      1"""
     )
 
 
 def test_metrics_diff_markdown_empty():
     assert _show_diff({}, markdown=True) == textwrap.dedent(
         """\
-        | Path   | Metric   | Value   | Change   |
-        |--------|----------|---------|----------|
+        | Path   | Metric   | Old   | New   | Change   |
+        |--------|----------|-------|-------|----------|
         """
     )
 
@@ -193,11 +192,11 @@ def test_metrics_diff_markdown():
         markdown=True,
     ) == textwrap.dedent(
         """\
-        | Path         | Metric   | Value   | Change             |
-        |--------------|----------|---------|--------------------|
-        | metrics.yaml | a.b.c    | 2       | 1                  |
-        | metrics.yaml | a.d.e    | 4       | 1                  |
-        | metrics.yaml | x.b      | 6       | diff not supported |
+        | Path         | Metric   | Old   | New   | Change   |
+        |--------------|----------|-------|-------|----------|
+        | metrics.yaml | a.b.c    | 1     | 2     | 1        |
+        | metrics.yaml | a.d.e    | 3     | 4     | 1        |
+        | metrics.yaml | x.b      | 5     | 6     | —        |
         """
     )
 
@@ -214,29 +213,10 @@ def test_metrics_diff_no_path():
         no_path=True,
     ) == textwrap.dedent(
         """\
-        Metric    Value    Change
-        a.b.c     2        1
-        a.d.e     4        1
-        x.b       6        1"""
-    )
-
-
-def test_metrics_diff_with_old():
-    assert _show_diff(
-        {
-            "metrics.yaml": {
-                "x.b": {"old": 5, "new": 6, "diff": 1},
-                "a.d.e": {"old": 3, "new": 4, "diff": 1},
-                "a.b.c": {"old": 1, "new": 2, "diff": 1},
-            }
-        },
-        old=True,
-    ) == textwrap.dedent(
-        """\
-        Path          Metric    Old    New    Change
-        metrics.yaml  a.b.c     1      2      1
-        metrics.yaml  a.d.e     3      4      1
-        metrics.yaml  x.b       5      6      1"""
+        Metric    Old    New    Change
+        a.b.c     1      2      1
+        a.d.e     3      4      1
+        x.b       5      6      1"""
     )
 
 
diff --git a/tests/unit/command/test_params.py b/tests/unit/command/test_params.py
index de55499cd..4c61c60ec 100644
--- a/tests/unit/command/test_params.py
+++ b/tests/unit/command/test_params.py
@@ -70,7 +70,7 @@ def test_params_diff_new():
     ) == textwrap.dedent(
         """\
         Path         Param    Old    New
-        params.yaml  a.b.d    None   new"""
+        params.yaml  a.b.d    —      new"""
     )
 
 
@@ -80,7 +80,7 @@ def test_params_diff_deleted():
     ) == textwrap.dedent(
         """\
         Path         Param    Old    New
-        params.yaml  a.b.d    old    None"""
+        params.yaml  a.b.d    old    —"""
     )
 
 
@@ -148,8 +148,8 @@ def test_params_diff_markdown():
         """\
         | Path        | Param   | Old   | New   |
         |-------------|---------|-------|-------|
-        | params.yaml | a.b.c   | 1     | None  |
-        | params.yaml | a.d.e   | None  | 4     |
+        | params.yaml | a.b.c   | 1     | —     |
+        | params.yaml | a.d.e   | —     | 4     |
         | params.yaml | x.b     | 5     | 6     |
         """
     )