Ancient Indian metallurgists made various major contributions to the metallurgical history of the world.
During the excavations, the archeologist found many things which show that the Harappans had knowledge of copper metallurgy. They were master craftsmen.
Even Bronze was manufactured by them by mixing copper and tin. Harappans belonged to the Bronze age.
Their successors belonged to the Iron age. During ancient times highly advanced types of iron-forged iron, wrought iron and cast iron was made in India.