ΔE 28.2, loose: different enough that you should pick on purpose. Gunmetal is noticeably darker, more muted than Necro Gold.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 28). Gunmetal is noticeably darker, more muted than Necro Gold.
The same difference applies the other way round: Necro Gold is noticeably lighter, 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.
See Necro Gold on the colour wheel See Gunmetal on the colour wheel
All matches: Necro Gold equivalents · Gunmetal equivalents