Abstract: A lightweight tailgate assembly for pickup trucks and other motor vehicles includes several metal panels that are made from a single metal sheet and a plastic reinforcing module between inner and outer metal panels. The side panels of the tailgate are formed as part of the plastic reinforcing module. A preferred assembly may also include a hinge device for connection with a truck body and a latch mechanism for locking the assembly between opposed rear corner posts in a truck body. The hinge device may be integrally molded into the plastic reinforcing module. A particularly preferred tailgate assembly made with AA 6022 aluminum alloy sheet and a reinforcing module containing polymer and glass fibers may weigh less than half as much as a conventional steel truck tailgate. Metal cover plates can be used to obscure visibility of the plastic side panels from the exterior.