Hot take: People still think you can just slap filler over rust and call it good
I mean, I see it all the time, especially on older cars people bring in. They'll grind the surface rust, throw a half inch of filler on it, and think it's fixed. It's not. That rust is coming back in under a year, guaranteed. I had a 2005 Silverado come through my bay last week where someone did exactly that, and the whole quarter panel was bubbling again. You gotta cut it out, weld in new metal, or at the very least use a proper rust converter and sealant. Who else has had to fix a hack job like this?