The ability to work metal into tools and other useful things was a major breakthrough for human industry. Metal tools enable people to process raw materials like food, fiber, or wood, and to manufacture useful items, like weapons and clothing. Metal weapons make available the Warrior and the Spearman, the first attacking and defensive units in the game.
The first evidence for human use of metal that they had shaped and changed from its natural state comes from Persia in about 5500 BC. There copper was smelted from malachite (copper carbonate). In succeeding centuries men learned how to work copper by casting it in sand molds or hammering it into shapes while heated or cold. No matter how it was worked, copper was and is too soft to hold a good edge, but it is harder and more durable than wood, leather, or reeds. Copper knives and axes, frequently resharpened, allowed workers to shape wood more easily. Copper spear and arrow points, axe heads and copper-weighted clubs increased the effectiveness of men in battle or the hunt. The same techniques used to work copper were also applied to lead, gold, and silver, making jewelers one of the earliest metalworking craftsmen.