How do I straighten my bent metal cupboard frame?
Nice cabinet by the way. I'm guessing it's a ferrous metal and if you hold a magnet to it the magnet is attracted to the metal. If so get your self a Mapp gas tank and a swirl-type torch. Heat the bent metal until it turns a dull red. Move the torch across the buckled area keeping the metal hot. Now with a smooth-face hammer (any style, 20-24 oz is best) begin tapping the bent metal back into shape. Start with light blows until you get a sense of how the metal is reacting to the hammer strikes. Re-heat as necessary.
If the metal is solid and not a tube you will need to apply heat for awhile. If you find the metal isn't moving under the hammer strikes heat it to a bright red or orange color. It may be easier to turn the cabinet on it's side or top to facilitate the pounding. Wear heavy gloves, eye protection and have a bucket of water close by.