In the fourth century B.C., bronze hydriae were embellished with a separately attached relief under the vertical handle. The subjects included scenes of abduction, Eros, or, as here, Dionysos, the god of wine, and his wife, Ariadne. The expensive vessels may have been given as wedding gifts and then used for special occasions. Many were placed in tombs, sometimes as containers for the ashes of the deceased.
von Bothmer, Dietrich. 1955. "Bronze Hydriai." The Metropolitan Museum of Art Bulletin, 13(6): pp. 198-9.