A governed performance metal shell bat designed to ensure ball exit speed approximating and not exceeding that of a wood bat of comparable weight and geometry is comprised of a thin wall metal shell filled such as aluminum or titanium or alloys thereof with light weight semi-rigid material such as a syntactic foam in the hitting area, the bat having longitudinal flexibility approximating that of a similarly shaped wood bat and the filler material having a density and hardness correlated with the thickness of the metal shell wall in the hitting area.