This refers to scripts found on ritual bronze artifacts. At the time, standardization of Chinese writing had not yet occurred and characters were written irregularly and in different orientations. Bronze inscriptions in the early days were cast using clay molds in which writing was written using a stylus. In later pieces, the bronze was often engraved after being cast.
There is no single bronze script. This script is distinguished from oracle bone scripts because of the medium and the complexity of the script. Different scripts were used stylistically by different nations during the Warring States period. Furthermore, scholars today believe that bronze scripts may have been considered more formal due to the conservative use of the medium.