Techniques for combining a polymer layer and a metal layer to form a multi-layer structure are disclosed. In one embodiment, an intermediate layer having pores, openings or voids is secured to the metal layer, and then the polymer layer is molded to the intermediate layer, whereby the pores, openings or voids in the surface of the intermediate layer serve to facilitate securing of the polymer layer to the metal layer. The multi-layer structure is suitable for use in as a portion of a housing for an electronic device, such as a portable electronic device.