ΔE 30.5, loose: different enough that you should pick on purpose. Silver RLM01 (Met.) is noticeably lighter than Tarnished Steel.
Can I use Silver RLM01 (Met.) instead of Tarnished Steel?
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 31). Silver RLM01 (Met.) is noticeably lighter than Tarnished Steel.
Can I use Tarnished Steel instead of Silver RLM01 (Met.)?
The same difference applies the other way round: Tarnished 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.