ΔE 40.3, loose: different enough that you should pick on purpose. Pearl Blue is a little darker, much more saturated, warmer than Cobalt Metal. They are different kinds of paint: Army Painter Cobalt Metal is a metallic and Tamiya Pearl Blue is a pearl paint, 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 40). Pearl Blue is a little darker, much more saturated, warmer than Cobalt Metal. They are different kinds of paint.
The same difference applies the other way round: Cobalt Metal is a little 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 Pearl Blue on the colour wheel
All matches: Cobalt Metal equivalents · Pearl Blue equivalents