ΔE 17.5, loose: different enough that you should pick on purpose. Obsidian Black is a little darker, much more muted than Cobalt Metal.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Obsidian Black is a little darker, much more muted than Cobalt Metal.
The same difference applies the other way round: Cobalt Metal is a little lighter, much more saturated.
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 Obsidian Black on the colour wheel
All matches: Cobalt Metal equivalents · Obsidian Black equivalents