Wash the furniture with a mild detergent and a sponge and rinse it with water.
Use a wire brush or steel wool to scrub the entire surface, paying special attention to areas with chipping paint or rust.
Apply a rust-dissolving solution, such as naval jelly, on iron and steel furniture with rust present. Let the solution sit on the furniture for between 10 and 15 minutes and then hose off the furniture. Allow the furniture to dry.
Apply one coat of spray primer designed for outdoor metal furniture. Use a rust-resistant formula, especially if you have had rust problems on the piece of furniture in the past. Allow the primer to dry per the manufacturer's instructions.
Spray the furniture with an exterior metal paint. For even coverage, use thin coats of paint by keeping the spray can in constant motion as you spray from side to side--this will also help avoid drips. Allow the first coat of paint to dry completely and then add a second coat.