Metal objects were brought over from the Asian continent in the early Yayoi period and the technology for casting such pieces was quickly mastered, enabling production in Japan. The ability to manipulate these metals is one of the characteristics that distinguishes Yayoi culture from that of the preceding Jômon period.

Iron was a strong metal suitable for farming and craft tools and for weapons, while bronze was used more to make ritual objects, such as mirrors, daggers and bells. The forms of these as well as the technology were copied from Chinese imported examples. However, cast metal did not completely displace the polished stone tools of the previous Jômon culture.

In order to cast pieces with complex designs people used either composite moulds made from several pieces of carved sandstone or specially made ceramic moulds. By about AD 300 smiths in the Japanese islands were able to replicate the intricate decoration on earlier Chinese mirrors. The most impressive metal item of the period was the ceremonial bell, or dôtaku. This was oval in shape with a flange running the length of the bell and a semi-circular handle. Many of the bronze spear-heads and daggers excavated appear to have had symbolic meaning in rituals rather than being used in real battles.