Porous metal foams are excellent engineering materials with dual attributes of structural and functional characteristics, and they may suffer shearing loads when they are used as engineering components. The mechanical behavior within the component is investigated for these materials under shearing loads, and the corresponding mechanical relationship is derived from mathematical-physical deduction, using a simple manner of segregating analysis. The results display that the maximal nominal shearing stress within the component can be described with the porosity of the porous body and the inherent characteristic parameters of the metal foam itself when it endures the fracture resulting from shearing loads. From this mathematical-physical relation, the strength criterion may be directly achieved for these materials under shearing loads.