A foam filled die cast metal baseball and softball bat has an all metal skin welded into a unit. The bat is formed by die casting the cylindrical handle and barrel of the bat in one piece and by welding an end cap to the cylindrical barrel to form the unitary skin structure of the bat. A foaming, sound-deadening and strengthening plastic material is then introduced into the hollow interior of the bat through an opening in the handle portion of the bat. The added material foams to fill the interior with a reinforcing semi-rigid foam. The bat has a steel safety rod embedded in the foam center of the bat. The end cap structure is formed of a roughly hemispherical cap and has a sleeve which fits into the interior of the barrel end of the bat. A shoulder on the cap abuts the bat end and extends outwardly radially past the periphery of the bat. The cap is joined to the barrel portion by resistance welding in a rotating lathe under an inert gas atmosphere.