Testors makes a great set of metal paints: gold, silver, copper, brass, rust, aluminum and steel. I use them but in very thin coats. They have a lot of surface tension so tend to hump up. You need to smooth them flat and add many thin coats. Search for my golden Iron Man figure in the Customs area. You can also mix and match the multiple layers, say adding one coat of brass or silver between gold layers to darken or lighten. Plus Testor's paints are cheap.