How to fix sheet metal holes?

There is alumafill or a steel type epoxy putty i used for some very small rust pinholes. My windshield guy suggested it, as they get some places where welding isnt feasable. Grind it, fill it,sand,prime and paint.
I have a customer who has used this product and he said it's just kind of like Bondo, but with metal flakes in it kind of smells the same...