ΔE 35.1, loose: different enough that you should pick on purpose. Ultramarine Blue is noticeably darker, much more saturated, warmer than Cobalt Metal.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 35). Ultramarine Blue is noticeably darker, much more saturated, warmer than Cobalt Metal.
The same difference applies the other way round: Cobalt Metal is noticeably lighter, much more muted, 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 Cobalt Metal on the colour wheel See Ultramarine Blue on the colour wheel
All matches: Cobalt Metal equivalents · Ultramarine Blue equivalents