Presented are protective covers for weldable fasteners, methods for making/using such cover-protected weldable fasteners, and motor vehicles with such covered fasteners welded to load-bearing structural members. A weldable fastener assembly includes a fastener, such as a weld-on nut or clip retainer, that is fabricated with a shank and a flange. One end of the shank has a fastener hole that receives therethrough a mating fastener, such as a bolt, screw, stud, or clip. The flange is formed, in whole or in part, from a weldable material for welding to a load-bearing panel or other structural support member. The flange may be integrally formed with and project radially outward from the shank. A protective cover is attached to the flange and covers the fastener hole. The protective cover is frangible and formed, in whole or in part, from a material designed to withstand the temperature at which the weldable material melts.