M M^m+ + m e^-

where M is a resident metal atom, M⁺ is a metal ion released to the electrolyte, and e^- is an electron.

For example, copper or nickel can oxidize to release 2 electrons each, and magnesium can oxidize to release 1 electron:

Different metals have different potentials, and their mutual ordering on the Electrochemical Series determines whether a particular metal will act as the anode (i.e. corrode) or act as the cathode. The more negative the potential, the more likely the metal is to corrode.