Surface modifications of metals and alloys by ion beams are discussed from the point of view of thermal oxidation. A brief description of a commercial ion accelerator and a few widely used ion sources are given. The microscopic processes such as recoil, collision cascades, and radiation-enhanced diffusion that accompany the ion beam processing are explained, and their consequences in oxidation studies are indicated. The complementary and confirmatory nature of methods of surface analysis in characterizing the modified surface before and after oxidation such as Rutherford Back Scattering and Nuclear Reaction Analysis are discussed. Application of ion beam modification to oxidation of metals and alloys is illustrated by several examples.