The present invention provides a method of forming a continuous one-piece structural porous metal (SPM) structure having a predetermined geometry. The method the invention includes the steps of preparing a metal billet comprising a metal core formed of a metal and a gas, and solid metal face sheets bonded to opposite sides of the metal core; placing the metal billet in a mold cavity having a predetermined geometry defined by opposing inner surfaces of the mold with at least one of the opposing inner surfaces contacting at least a portion of the metal billet and spaced apart from at least a portion of the metal billet; and heating the metal billet to expand the metal core to form the expanded metal structure. The portion of the metal billet in contact with the inner surfaces of the mold cavity is constrained by these surfaces while the remainder of the metal billet that is spaced apart from at least one of the inner surfaces of the mold is allowed to expand resulting in a one-piece expanded metal structure having a geometry corresponding generally to the geometry of the mold cavity with the constrained portion of the metal structure having a higher density than the remainder of the expanded metal structure. The present invention also includes a continuous one-piece expanded metal structure.