Metallurgy was discovered around 4000 BC allowing for the extraction of metals from ores for processing. Society progressed through the Copper, Bronze, and Iron Ages as metalworking techniques advanced. During the Metal Ages, settlements grew in size and complexity with circular or rectangular dwellings surrounded by palisades. Economies centered around agriculture using new metal tools, livestock, trade, and specialized labor roles like metal artisans. People worshipped nature gods and held ceremonies. Defense structures like walls were built to protect villages from conflict and war. In Spain, important Metal Age cultures included the Copper Age Millares and Bell Beaker cultures, the Bronze Age El Argar culture, and the Bronze Age Talaiotic culture