Motherlode vs Copper (Metallic)

How close are they?

ΔE 17.9, loose: different enough that you should pick on purpose. Copper (Metallic) is a little lighter, more muted than Motherlode.

Can I use Copper (Metallic) instead of Motherlode?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Copper (Metallic) is a little lighter, more muted than Motherlode.

Can I use Motherlode instead of Copper (Metallic)?

The same difference applies the other way round: Motherlode is a little darker, 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.