ΔE 20.0, loose: different enough that you should pick on purpose. Rusty Metal is a little lighter, much more muted, warmer than Brass.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Rusty Metal is a little lighter, much more muted, warmer than Brass.
The same difference applies the other way round: Brass is a little darker, much more saturated, cooler.
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 Brass on the colour wheel See Rusty Metal on the colour wheel
All matches: Brass equivalents · Rusty Metal equivalents