Etruscan jewelry
The combination of metals was a basic technique. Essentially, there is no such thing as 24 carat gold jewelry. Massive gold is the most malleable metal. It is almost like wax. In order to have jewelry that can pass the test of time and gravity, the Etruscans had to combine their gold with other metals.
DFM Guidelines for Hot Metal Extrusion Process
Nowadays, quite a wide variety of metals are currently extruded commercially, the most common are (in order of decreasing extudability): Aluminium, Magnesium and their alloys, Copper and Copper alloys, low-carbon and medium-carbon steels, low-alloy steels and stainless steels. So obviously as the extrudability decrease the cost of production increases