You can use automotive body fillers on properly prepared steel or aluminum trailer bodies. Depending on the type of repair, different materials are used. If you have rust through, the size of the hole will determine what type of repair is necessary. Pin holes and up to a dime sized hole can be covered with fillers and epoxies, anything larger should have new metal patches installed.

The types of fillers will vary from the polyester cream types to fiberglass and aluminum reinforced materials. Small holes can be filled with the small epoxy kits mentioned above or the two part "liquid metals" like JB Weld. The fillers are then spread over the repaired area to provide the smooth paintable surface.

The most important step in a steel repair is the usage of a metal rust converter. Without it, the rust will continue and the repair will fail.

These products are commonly purchased at most automotive parts suppliers.

BOL  Gard