# Clean it. Because outdoor furniture is left to the elements for long period of time, it can get pretty grimy. Use a deep-cleaning product like BioWash or Oxyclean on dull or dirty plastic furniture.
# Buff it with steel wool. If you have unpainted metal furniture that's looking a little rusty, scrubbing it with steel wool can be an effective way to remove rust and bring out the shine underneath.
# Spraypaint it. Quick, easy, and cheap, spraypaint works well on metal and wood. You can also buy special spraypaint for plastic furniture.