The metal is plastically deformed under compression in the die cavity. Extrusion processes can be carried on hot or cold materials.
Extrusion differs from drawing in that the metal is pushed, rather than pulled under tension.
Typically setup cost for extrusions are expensive. This due to tooling cost and setup. Actual manufactured part cost is inexpensive when produced in significant quantities. Tight tolerances' are not typical to the extrusion process. Materials that can be extruded are copper, brass, aluminum, steel, plastic and others.