Also if its a grille type you might want to keep a hair dryer handy to blow out the paint from the grilles so they don't clog up and close the holes up, but don't put any heat on it, let the paint dry naturally.
I'm partial to epoxy rattle can paint for things like this. It is very durable and goes on smooth. You might want to take some surface temperature measurements of your cage and make sure whatever paint you choose can handle the temperatures.