Abstract The metallurgy of the casting alloys is presented here according to bifilm theory. At the time of writing this chapter, the bifilm interpretation is more speculative than I would like, but it is a theory which fits the facts with uncanny accuracy. The light alloys based on Mg and Al are soundly explained by the bifilm approach. Zinc alloys, cast irons, steels, nickel and titanium alloys all exhibit structures and behaviour explicable by bifilms which effectively control mechanical and corrosion properties.