Who was Zeus's first wife?

Answer 1

Mètis was the first great spouse of Zeus, indeed his equal (Hesiod, Theogony 896) and the mother of Athena, Zeus' first daughter, the goddess of the arts and wisdom. By the era of Greek philosophy Mètis had become the goddess of wisdom and deep thought.

Mètis was both a threat to Zeus and an indispensable aid (Brown 1952:133):Zeus lay with Metis but immediately feared the consequences. It had been prophesied that Metis would bear extremely powerful children: the first, Athena and the second, a son more powerful than Zeus himself, who would eventually overthrow Zeus.[2]

In order to forestall these dire consequences, Zeus tricked her into turning herself into a fly and promptly swallowed her.[3] He was too late: Mètis had already conceived a child. In time she began making a helmet and robe for her fetal daughter. The hammering as she made the helmet caused Zeus great pain and Prometheus, Hephaestus, Hermes, or Palaemon (depending on the sources examined) either clove Zeus's head with an axe,[4] or hit it with a hammer at the river Triton, giving rise to Athena's epithet Tritogeneia. Athena leaped from Zeus's head, fully grown, armed, and armored, and Zeus was none the worse for the experience. The similarities between Zeus swallowing Mètis and Cronos swallowing his children have been noted by several scholars.

Another View

Zeus's first and only wife is Hera. The others were all "affairs" and do not constitute as being married.