ΔE 18.7, loose: different enough that you should pick on purpose. Rusty Metal is noticeably lighter, warmer than Iridescent Bronze (Fine). They are different kinds of paint: Golden Iridescent Bronze (Fine) is a pearl paint and Vallejo Rusty Metal is a metallic, so they won’t behave the same on the model even where the colour is close.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Rusty Metal is noticeably lighter, warmer than Iridescent Bronze (Fine). They are different kinds of paint.
The same difference applies the other way round: Iridescent Bronze (Fine) is noticeably darker, 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 Iridescent Bronze (Fine) on the colour wheel See Rusty Metal on the colour wheel
All matches: Iridescent Bronze (Fine) equivalents · Rusty Metal equivalents