Mixing metals, like mixing wood tones, is something that requires confidence. But with the near ubiquity of warm metals in recent years, it's likely that your home already hosts a mix of metals.
Recent accessories I've brought in copper and brass, while older fixtures and hardware are polished nickel. It's unlikely I'll ever get it all synced and I really don't think that's even a necessary goal. Copper, brass, silver and gold - they're all beautiful in their own right and really I think individual objects (and jewelry) should dictate their own individual beauty.
Right now, these speak to me. But that doesn't mean you couldn't also turn my head with some classic Georg Jensen silver. It's a good thing I have such a big heart, I guess!