Dave gives great advice. I used the metal 2 metal only a few times and I can't even remember what it was on. I think it was a welded seam line on a 72 Charger R/T and I cannot remember the other ones. I only used it in medium to light coats and never built it up too much because like Dave mentioned, it gets so hard that it's a pain to cut down and it will chip. As for brands, I am with Dave on this as well, Evercoat makes the best or workable products as far as fillers go IMO. I use their Rage Gold bondo, their glaze in the little squeezable tube deal, and their fine strand kitty hair (this may not be the correct name but it's what I call it and I like the fine hair for mostly what I do).