ΔE 16.8, loose: different enough that you should pick on purpose. Bare Metal Silver is noticeably lighter than Ironbreaker.
Can I use Bare Metal Silver instead of Ironbreaker?
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Bare Metal Silver is noticeably lighter than Ironbreaker.
Can I use Ironbreaker instead of Bare Metal Silver?
The same difference applies the other way round: Ironbreaker is noticeably darker.
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.