The die must fulfill four primary purposes. First, it must hold molten metal in the shape of the final casting. The die must also provide a path for the molten metal to reach the casting cavity. Third, the die is designed to remove heat from the casting. Finally, a die must be able to eject the solidified casting.

Because die sets open and shut along a parting line of the casting, design features such as undercuts cannot be cast without the addition of movable slides in the die set. Otherwise these features must be added (more expensively) by secondary machining operations.

Die casting machines are rated by how much clamping force they can apply. Typical sizes range from 100 to 4,000 tons. Along with size there are two main categories that die casting machines fall into. They are hot chamber machines for zinc and lower melting-point metals. Or cold chamber machines for aluminum and higher melting-point metals. A die casting machine automatically opens and closes the mold and injects the liquid metal, all under high pressure and as rapidly as possible, in the case of zinc up to several hundred times an hour. (However the very smallest zinc machines may cycle thousands of time an hour.) Sometimes means are provided to automatically remove the shot and re-cycle the machine. The largest machines are as big as a car.

Often there is a secondary operation to separate the castings from the scrap; this is often done using a trim die in a power press or hydraulic press. An older method is separating by hand or by sawing, which case grinding may be necessary to smooth the gate mark where molten metal entered or left the cavity. Finally, a less labor-intensive method is to tumble shots if gates are thin and easily broken. Separation must follow.

Most die casters perform other secondary operations to produce features not readily castable. Most common is tapping a hole (to receive a screw).

Or the surface may be improved; for example, polishing and buffing. Or plating or painting.