ΔE 19.3, loose: different enough that you should pick on purpose. Rusty Metal is much more muted, warmer than Copper.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Rusty Metal is much more muted, warmer than Copper.
The same difference applies the other way round: Copper is 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 Copper on the colour wheel See Rusty Metal on the colour wheel
All matches: Copper equivalents · Rusty Metal equivalents