Casting is the earliest known form of liquid metal processing and is still an important process today. Casting is the introduction of molten metal into a cavity or mold where, upon solidification, it becomes an object whose shape is determined by mold configuration. Casting offers several advantages over other method of metal forming: it is adaptable to intricate shapes, to extremely large pieces, and to mass production, etc.

Two broad categories of metal-casting processes exist: ingot casting (which includes continuous casting) and casting to shape. Ingot castings are produced by pouring molten metal into a permanent or reusable mold. Following solidification these ingots (or bar, slabs, or billets) are then further processed mechanically into many new shapes. Casting to shape involves pouring molten metal into molds in which the cavity provides the final useful shape, followed only by machining or welding for the specific application.

Casting processes include sand casting, permanent-mold casting, die casting, centrifugal casting and continuous casting etc.