ΔE 19.7, loose: different enough that you should pick on purpose. Blue Steel is noticeably darker, much more saturated than Plate Mail Metal.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Blue Steel is noticeably darker, much more saturated than Plate Mail Metal.
The same difference applies the other way round: Plate Mail Metal is noticeably lighter, much more muted.
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 Plate Mail Metal on the colour wheel See Blue Steel on the colour wheel
All matches: Plate Mail Metal equivalents · Blue Steel equivalents