ΔE 29.1, loose: different enough that you should pick on purpose. Bright Brass (Met.) is noticeably lighter than Natural Steel.
Can I use Bright Brass (Met.) instead of Natural Steel?
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 29). Bright Brass (Met.) is noticeably lighter than Natural Steel.
Can I use Natural Steel instead of Bright Brass (Met.)?
The same difference applies the other way round: Natural Steel 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.