We find that the simple reaction-dissociation of O2-supported on metal surfaces can profoundly account for the oxidase-like activities of the metals. Using density functional theory (DFT) calculations, we investigate mechanisms of oxidase- and SOD-like properties for metals Au, Ag, Pd and Pt and alloys Au4-xMx (x = 1, 2, 3 M = Ag, Pd, Pt). However, origins of these activities remain to be studied. Metal and alloy nanomaterials have intriguing oxidase- and superoxide dismutation-like (SOD-like) activities.