Old Gold vs Aged Metal

How close are they?

ΔE 27.7, loose: different enough that you should pick on purpose. Aged Metal is noticeably darker, cooler than Old Gold.

Can I use Aged Metal instead of Old Gold?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 28). Aged Metal is noticeably darker, cooler than Old Gold.

Can I use Old Gold instead of Aged Metal?

The same difference applies the other way round: Old Gold is noticeably lighter, 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.