Rustoleum manufacturers paint and primer and offers a product line specifically for covering and protecting metal surfaces. They can be used on metals that are rusty, provided you prepare the surface so the primer or paint properly adheres to it. The primer and paint also protects the metal from further rusting. Before you start with your project, lay down newspaper or a drop cloth to protect the floor or ground and make clean up easier.
Clean the metal with a household cleaner or just plain hot, soapy water. You can also use trisodium phosphate (TSP) for heavy dirt, grime and grease, but dilute with water as the label indicates and use a sponge or rag to clean. Rinse with water or a wet rag.
Remove loose rust with a wire brush, steel wool or a scraper. This also removes old, chipping paint, if applicable. If the current finish is glossy, sand it with fine sandpaper. If you're working with lead paint, do not sand it, according to Rustoleum's website.
Rinse the metal clean with water. Use a wet rag instead, rinsing it out frequently, if you can't clean the metal with your hose or another source of running water, such as a utility sink. Allow the metal to dry before painting.
Prime and then paint with a Rustoleum metal primer and paint, respectively. Apply a thin coat with a brush or roller. If you spray it on, shake the can for about a minute and spray it in even parallel sweeping motions starting at the top, holding the can about 8 to 12 inches away.
Allow the primer or paint to dry between coats as indicated on the label. Drying times vary among products and current air temperatures. You may need a second or third coat of paint to adequately cover the surface, especially if you're spraying it on.