Abstract: A module for building structure includes a moment frame, a set of four top corner pieces, and a set of two or more composite panels. The moment frame is comprised of beams and columns jointed to form a top, a bottom and four sides. Each top corner piece is located at a corner of the top of the moment frame. The set of two or more composite panels is attached to the bottom of the moment frame to provide a sub-floor of the building structure. A first composite panel, of the set, is adapted to transfer a load to a second abutting composite panel of the set, in response to a deflection of the moment frame. Each composite panel is comprised of a core element encased in a metal frame, which includes two face sheets, two end cap pieces, and two side pieces.