The requirements which have been placed on metallization for silicon integrated circuits are listed and their origins are traced. Physical models relating to various requirements are discussed. Among these are oxygen activity as a criterion for adherence, slope etching, impurity effects on resistivity, self‐shadowing effects on step coverage, and Schottky barrier formation and tunneling as a determinant of contact resistance. The procedures necessary for optimization of some of these properties are considered. Physical vapor deposition methods are reviewed and compared. The more demanding problems of interaction with silicon at contacts, electromigration‐induced failure, two‐level metallization processing, and corrosion are discussed at length. Approaches designed to allow a basically aluminum metallization to meet all requirements are presented. It is concluded that the use of aluminum alloys is the most generally beneficial technique and that additional effort must be devoted to defining a fully satisfactory method for corrosion protection.