[fauXGT]

Several manufacturers of the metal filler, but simply put it is the replacement for exterior panel seam seal instead of lead solder between body parts. It actually has bits of aluminum (or aluminium.. however you pronounce it) in the filler. It says on the label that it is for small pinhole filling, and not structural.
I first found 'All metal' at the local Napa, then they switched to Evercoat, but it will still fill the tiny holes, sand, then prime and paint. I recommend painting or POR'ing both sides of the surface after filling and sanding.