Remove any cushions from the furniture. Set them aside.
Scrub away any rust spots with a wire brush. If the furniture already has a coat of paint, check for any chipped areas. Sand them down with fine-grit sandpaper until the spots are smooth and there are no rough edges.
Fill a bucket with warm water and a squirt of liquid dish soap. Dip a clean cloth into the soapy water. Wipe down the furniture to remove any sanding dust. Rinse the cloth. Wipe the furniture again to remove the soap residue. Wipe the piece with a dry, lint-free cloth.
Move the piece of furniture to a shaded spot. Sit it on top of pieces of cardboard to protect your patio.
Fill a paint tray with an exterior primer. Paint the entire surface of the furniture with a coat of exterior primer, using a small paintbrush. Let it dry according to the directions on the paint container.
Rinse out the paint tray and let it drip-dry while the primer dries. Open a can of exterior metal paint and stir it with a paint stirrer.
Paint the entire surface of the furniture with the exterior metal paint. Let it dry according to the paint manufacturer's directions. Add another coat if the color is not dark enough.