Clean the metal with rubbing alcohol. If the metal has rusty spots, be sure to sand them out as rusted metal will not hold paint.
Decide if the texture is important or if you would like to cover it as much as possible to make the surface appear flatter.
Cover the metal with a base coat of primer. If you want cover the metal's texture, apply a heavy-bodied paint with a thick brush to help fill in the recesses. If you want the texture to remain, thin the base coat with water or paint thinner to allow it to penetrate the metal's cracks and crevasses more easily.
Paint the metal with two or three or coats of paint. Check the directions on the paint's container and allow the paint to dry completely between coats.
Repeat step 4 until the desired effect is achieved.
Seal the painted metal with your preferred clear coat. A glossy clear coat will give the metal a shine, and a matte clear coat will make the color appear dull and natural.