ΔE 38.4, loose: different enough that you should pick on purpose. Deathless Metal is noticeably darker, much more muted, cooler than Fulgurite Copper.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 38). Deathless Metal is noticeably darker, much more muted, cooler than Fulgurite Copper.
The same difference applies the other way round: Fulgurite Copper is noticeably lighter, 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.
See Fulgurite Copper on the colour wheel See Deathless Metal on the colour wheel
All matches: Fulgurite Copper equivalents · Deathless Metal equivalents