An overview is provided on the properties and growth of passive films on Fe group metals and stainless steel. The growth kinetics of passive film might be explained by the Cabrera-Mott theory with some modifications. Passivation of stainless steel is characterized by Cr enrichment in the film with some critical Cr content above which the “stainless” passive film is obtained. The existence of the critical content is explained by using a percolation model and a competitive precipitation model. Modification of passive films is also described in terms of obtaining the much higher corrosion resistance and the surface functions.