ΔE 22.1, loose: different enough that you should pick on purpose. Rusty Metal is a little darker, much more saturated than Sparkle Motion.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Rusty Metal is a little darker, much more saturated than Sparkle Motion.
The same difference applies the other way round: Sparkle Motion is a little lighter, much 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 Sparkle Motion on the colour wheel See Rusty Metal on the colour wheel
All matches: Sparkle Motion equivalents · Rusty Metal equivalents