By means of the interface reactions of Mo(W)S42- on a metal (copper, steel, zinc, silver, nickel, tin) surface, insoluble cluster compound films were formed with a metallic luster of various colors changing in accordance with the reaction time. The films are functional finishing layers, possessing not only decorative properties, but improving the brightness and cleanliness of the metal surface, and promoting the anticorrosive ability of the metals as well. Their colors are probably caused by Mo (W)-S-M (M= Cu, Fe, Zn, Ag, Ni, Sn) bonds and a statistical distribution and overlapping of various molecular layers, inasmuch as the films are complex multicomponent and smultilayer systems. Accelerated corrosion tests, LSV, CV, FT-IR, FT-Rmamn; XPS and AES determinations were carried to investigate composition and structure of these conversion films. The results show that bridged Mo(W)-S-M, terminal Mo(W)-S and terminal Mo(W)-O bonds exist in the cluster compound films. The mechanism for films formation and the relationships between these novel films structure and the observed inhibition behavior are discussed.