Bright Gold vs Molten Bronze

How close are they?

ΔE 34.1, loose: different enough that you should pick on purpose. Molten Bronze is noticeably darker, much more muted, warmer than Bright Gold.

Can I use Molten Bronze instead of Bright Gold?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 34). Molten Bronze is noticeably darker, much more muted, warmer than Bright Gold.

Can I use Bright Gold instead of Molten Bronze?

The same difference applies the other way round: Bright Gold is noticeably lighter, much more saturated, 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.