You’re better off with a MIG
I recently picked up a Lincoln fluxcored wire welder. Can I use this type of welder for sheet metal repair?
Yes, you can use flux-cored wire for automotive sheet metal but it usually is not the best choice.
A MIG welder with a solid metal wire electrode and shielding gas generally will produce cleaner welds, create a smaller heat impacted area, and reduce the likelihood of burning through the sheet metal. The primary advantages of flux-cored wire is that it’s easier to use outside in windy conditions, generally does better with contaminated metal because they usually contain de-oxidizing elements that trap rust, mill scale, oil, and similar contaminants in the weld pool and hold them in the slag, increases penetration of the weld’s side walls, and provides greater weld metal deposition. None of these advantages pertain to automotive sheet metal work, which should be done indoors with clean metal.
Flux-cored wire welding is generally more suited to heavy, outdoor welding such as pipe work, on-site large truck and equipment repairs and the like.