The effects of substrate bias on the electrical resistivity, accumulation rate, and impurity content of metal films deposited by rf and dc sputtering have been investigated. Some experimental techniques are described which make it possible to separate the effects of bias on resputtering, plasma density, and substrate temperature. The accumulation rate data as a function of bias have been analyzed in terms of a semiempirical equation. The analysis has elucidated the relative importance of bias-induced resputttering and plasma density changes in rf and dc sputtering.