This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Metal Branches gathers the two of the twelve Earthly Branches whose own fixed agent is Metal: Shen the Monkey and You the Rooster, the branches that open and then crown the autumn.
Shen, the ninth branch, opens the seventh solar month at the Start of Autumn and governs the hour from three to five in the afternoon, in the west-southwest. It is a growth branch, storing Geng as its principal qi alongside Ren and Wu, so Shen carries the birth of Water concealed inside its own hardening Metal; as the branch that opens the Water trine, it marks the first turn of the year toward autumn's harder, cooler qi. You, the tenth branch, sits at the autumn equinox and governs the hour from five to seven in the evening, seated due west. It is a pure cardinal branch, storing only Xin, so its concealed qi and its surface agree without the mixed stems a storehouse branch carries; as the cardinal Metal it anchors the Metal trine it forms together with Si and Chou, and it is read as the clean, polished blade of the harvest.
Between them the two Metal branches trace autumn's whole arc, from the first hardening Shen carries, with its hidden capacity to generate Water, to the sharp, refined Metal You brings to its height. Both, like every branch, began as day-count signs in the oracle-bone tradition, numbering a sixty-day cycle together with the ten Heavenly Stems before either carried the animal now attached to it.