Welder for body metal

Adding gas to a mig welder will make a world of difference. For steel use 75% argon with 25% carbon dioxide.

Also a "trick" that helps with welding sheet metal is to have a copper or aluminum backing plate. It doesn't have to be big just hold it against the back of where your welding. The backing plate will keep you from blowing holes in the metal. My backing plate is a aluminum concrete edging tool with the edge cut off.