The most permanent repair to a hole in sheet metal is to weld the hole shut.
Rusty thin sheet metal blowing holes welding.
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.
Try applying that technique to steel less than 1mm in thickness and you are likely to blow a hole in the metal.
Stick welding sheet metal with 6013 rods.
This is the thinnest sheet metal i have ever welded using this process.
Any kind of welder can be used but the best results come from a competent repairman using a tig or mig welding machine.
The photo is 1mm steel welded at a power setting normally reserved for 2mm steel.
The butt weld page showed how to do a seam weld using a continuous torch movement.
The easiest holes to fill are small holes about the diameter of a pen or smaller.
Make sure to use an electrode wire that is thinner as it uses lesser heat and prevents blowing holes on to the sheet metal.
For these types of holes i start by cleaning the area around the hole with an angle grinder and flap disc.
A rust hole compromises the structural integrity of the metal.
Try going for a wire of 023 inches when welding sheet metal.
Try welding with a scrap sheet metal piece and practice many times until you start working on more important projects.
Video of the day.
Two part epoxies are designed for this purpose and when applied to a clean surface the final repair will be undetectable after painting.
The complexity of welding increases as the thickness of the material decreases.