Remove general soil and grit with detergent and water. With steel wool, emery cloth or a wire brush, remove all loose peeling paint and rust. Wipe surface using cloth dampened with turpentine or vinegar.
If the metal is bare, you have an option of coating the metal so the molecular structure changes to a rust resisting blue-black finish. See your paint, home center or hardware store for these specialty products.
No paint will stick to a greasy or wet surface. First coat should be a "metal primer" or "rust retardant" type paint. Second coat can be of enamel or paint suitable for place item is to be used, usually outdoor enamel. Exterior house and trim paints normally dry to soft for this use. When painted surface is completely dry (a couple days) in some cases you may apply protective finish as if item were new. Check with the product you are using for best results.
Small chips or scratches should be touched up immediately with primer followed by matching paint to prevent rust forming
This article has been contributed in part by Michigan State University Extension