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