Before you attempt to paint a metal fireplace, understand a pair of important factors. First, because metallic surfaces are nonporous, you must abrade them to promote adequate paint adhesion. Unfortunately, metal's durability makes friction-based abrasion methods impossible. You'll have to apply a special kind of primer that will etch the metal before you paint. In addition, because fireplaces generate a lot of heat, choose a specific kind of paint capable of withstanding high temperatures.
Scrub the fireplace with a degreaser, using a coarse brush. Rinse the metal with wet rags. Allow the surface to dry.
Apply painter's tape to portions of the fireplace you want left unpainted. Cover larger areas below the fireplace with dust sheets.
Apply a light coat of galvanised metal etching primer to the metal fireplace, using a 3- to 4-inch latex paintbrush. Apply only a light coat. Do not overapply as this may lead to runs and brushstrokes in the final finish. Allow the primer to dry and cure for four hours.
Wash the paintbrush with water.
Apply two light coats of epoxy appliance paint to the primed fireplace, using the paintbrush. Apply in the same way you did the primer. Allow two hours of dry time between coats.
You can also use spray cans of etching primer and appliance paint. However, thoroughly cover areas adjacent to the fireplace with masking paper and painter's tape to prevent unwanted paint overspray. Ensure that the metal fireplace is completely cool before starting.
Never attempt to paint a metal fireplace without applying a galvanised metal etching primer first. Do not use plain primer in place of galvanised metal etching primer, or the finish will chip away. Do not paint a metal fireplace with an ordinary paint, or the finish may bubble and peel because of high heat.