Prime the cabinet with oil-based, rust-inhibitive primer. Since manufacturer's instructions vary between products, check for specific directions on application and drying procedures.
Paint the cabinet a color that complements the rest of your decor choices. If using a metal cabinet as extra storage in an Asian inspired dining room, choose a bright red paint or coat it with a calming blue for an ocean-themed bathroom.
Paint separate areas on the cabinet different colors for an interesting pattern. If the sides and top of your cabinet is black, paint the door white for a visual pop.
Change out the handle for a more interesting one if you can. Some metal cabinets have welded in drawer and door pulls that need to just be painted to match because they cannot be taken out.
Attach magnets to the metal cabinets to cover any unsightly areas or to add more color and pattern to the design. Use a collection of fruit magnets in a traditional kitchen or colorful clothespin magnets to hold notes in a home office area.
Change out any plain padlocks on the cabinets to more colorful ones. For example, put a hot pink one on the drawer that you daughter keeps her diary in or a camouflage one if the cabinet is going to be placed in your son's military themed room.
Bring on other metal accessories when decorating with metal cabinets. For example, sit a DIY metal sculpture on top of the cabinet if it's in a foyer or place a collection of chrome vases holding your favorite bouquets if it is being used as extra storage in your bedroom.