Rattle can over Metal Patch Body Filler? is it safe?

[mahanian]

If you self etched the bare metal I don't see the need to do it again. If you are wanting to protect it from water because you plan to leave it primered for awhile your best bet would be an epoxy primer. In my opinion the primer will make or break a paint job, so this is not the point to cut corners. I would buy a quality epoxy primer and seal up all the metal work. You can use a builder/filler primer later down the road before you block sanding and paint. Filler primer holds moisture and will not seal up your metal work.