Metal furniture collects dust and dirt just as easily as any other furniture and should be cleaned regularly to maintain its appearance and avoid rusting. Whether your metal furniture is used indoors or outdoors, it will benefit from a regular cleaning routine to remove any accumulated debris.
A simple way to clean your metal furniture:
Combine three tablespoons of liquid dish-washing soap with warm water in a bucket. 
Dip a nylon scrub brush into the warm, soapy water and scrub the entire surface of the piece of furniture, using a smaller brush for corners and crevices, if needed. 
Rinse the piece of furniture with clean water.
Wipe the furniture dry with a towel.

While you are cleaning your furniture, it is a good idea to spot treat any rusted spots on the piece. To remove rust spots, scrub them with a wire brush until all of the rust flakes off.