there are a bunch of different paints available. depending on what you want to do with it. I would not suggest spraying directly to metal as you might have some corrosion problems down the road. all bare metal should be primed or treated before applying color. auto colors is a water based air brush paint that works well. AOE carries a wide selection of that brand. you can use regular automotive paints just over reduce them so that they flow through the tiny tip of that gun better.

Josh