ΔE 13.4, fair: the same colour family, but not a straight swap. Natural Steel is noticeably darker than Heavy Metal.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Natural Steel is noticeably darker than Heavy Metal.
The same difference applies the other way round: Heavy Metal is noticeably lighter.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Heavy Metal on the colour wheel See Natural Steel on the colour wheel
All matches: Heavy Metal equivalents · Natural Steel equivalents