Go to a sheet metal shop, get you some sheet metal clippers a rivet gun and go to town.
Cut out rusty spots. Chicken wire, fiberglass and Bondo easier to work with, and will look better, too.
Use a steel brush before you apply a cover compound.
I have a 1996 f150 and it is only my second vehicle to do some work around the house. I do have.some rust spots that I would like to cover up with sheet metal but I'm unsure how or where to even get it. Does anyone know. And I also could care less how awful it looks I'm just using it for things my car can't do. Thank you