Thanks to modern chemistry and manufacturing we now have two part epoxy panel adhesives that are strong and flexible enough to bond metals together more or less permanently.
How to repair sheet metal door rust.
Cut some sheets of masking paper to size with a sharp pair of scissors.
How to repair rusted metal without welding.
Sand the damaged area use sandpaper or a sanding block to remove any existing rust or paint from the damaged area.
Pull the trigger of the angle grinder and run the spinning 60 grit flapper wheel over the rusted area of the metal.
The area should be sanded until it.
Leave the rusted area exposed.
Cover the surrounding metal with masking paper and tape.
The most permanent repair to a hole in sheet metal is to weld the hole shut.
Specially formulated metal primers are designed to help prevent future.
The welding process actually adds new steel to the thin steel and can result in a repaired spot that is stronger than the original metal.
The complexity of welding increases as the thickness of the material decreases.
Apply metal paint primer to your door with a paint roller for the larger areas and a paintbrush for crevices and grooves.
I had a major rust problem in my 1989 mitsubishi montero ls v 6 four door and thought giving glue a chance would at worst demonstrate what not to do and at best bond some new steel in place of rust with a minimum of body filler.