The manufacture of cellular metals in the most general sense, as described in published works,1 does not always involve foaming methods. Often, a polymer foam is first opened by a special treatment and then replicated to yield a metallic structure. Replication can be carried out by coating with metal vapor, electroplating, or investment casting. The result is a structure with open porosity— a sponge rather than a foam. The physics of foaming has nothing to do with the metallic state because only the polymer precursor was foamed. Other structures can be used as templates for creating cellular materials: loose or sintered bulks of inorganic or organic granular matter, hollow spheres, or even regular polymer structures which are converted to a metallic structure in a designated processing step. In contrast, true foaming methods do not use a template for obtaining the special morphology; the metal is self-forming during foaming.