Prepare a metal awning for painting by thoroughly cleaning it of debris, sanding it and removing any mildew or mold present. Tape the edges of the awning to avoid paint splatter. Apply a primer prior to applying the first coat of paint.
To remove dirt and debris from the awning prior to painting, use soap in conjunction with a high-pressure hose. Remove the remaining stains with a mixture of bleach and water applied with a spray bottle. Allow the solution to sit for at least 10 minutes before removing it with a sponge. Repeat as necessary until the solution removes all stains. Thoroughly rinse off the bleach mixture.
Smooth the awning's texture by sanding it using sandpaper or a wire brush. Finish sanding after achieving an even texture over the entire surface. Prior to painting, cover nearby areas using plastic sheeting and painters tape to protect surrounding structures, plants and ground from splatter.
Using a paint roller, coat the awning with a primer designed for outdoor materials that also prevents rust and corrosion. For the outer coatings, choose a paint designed for outdoor metal surfaces, such as an acrylic latex or a spray paint. Apply two coats, allowing for proper drying between each. After the final coat dries, sand the roof as needed to create an even texture.