I believe there are some styles that are long the gold foil look. There are also tutorials on youtube about it. But basically it is a sharp contrast between highlights and shadows with a color overlay. Using a gradient that goes from bright to dark and bright again which can be repeating, would create that contrast. As long a the gradient is grayscale, a color overlay will change it from god to silver for example. Yellowish for gold and white for silver. This could also be used for brass.
Adding a texture could change it even more from a polished metal to a rough metal.
Good luck...