Silver is meant to be used against all unnatural beings (demons, witches), while iron kills the supernatural (fae).
Gold is less specific, but it's had holy context for ages. On the other hand, it eventually came to symbolize greed and corruption, but I've never seen it have anything like silver or cold iron does.
Well, I've seen it in Hellboy (1st movie) where his bullets are a mix of holy water, garlic and some metal and in Constatine (Keanu Reeves ftw) uses a golden shotgun with "holy bullets", which I assume gold is also involved.
Tbh, I'd expect almost all magic to outweigh the innate properties of something. Maybe silver/gold could be strong enough to burn or purify a zombie or something, but a vampire would be fine decorating themselves in fine jewelry, especially if they wanted to make a mockery of the holy.
Gold is less specific, but it's had holy context for ages. On the other hand, it eventually came to symbolize greed and corruption, but I've never seen it have anything like silver or cold iron does.