Metallic Green vs Beetle Green

How close are they?

ΔE 37.3, loose: different enough that you should pick on purpose. Beetle Green is much more muted, cooler than Metallic Green.

Can I use Beetle Green instead of Metallic Green?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 37). Beetle Green is much more muted, cooler than Metallic Green.

Can I use Metallic Green instead of Beetle Green?

The same difference applies the other way round: Metallic Green is much more saturated, warmer.

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.