The poet Hesiod revealed the identity of the parents and siblings of Metis in a portion of a beautiful passage of his Theogony:
"Metis, Eurynome, and saffron-robed Telesto,
These are the eldest daughters born to Tethys and Okeanos."
According to Hesiod, Metis is therefore the daughter of the Titans Okeanos (Oceanus) and Tethys. Her sisters, who are called Oceanids in honor of their father, include such famous mythological figures as Doris, Calypso, Styx, Perseis, and Tyche.
"Zeus, king of the gods, took as his first wife Metis,
a mate wiser than all gods and mortal men.
But when she was about to bear gray-eyed Athena,
then through the schemes of Gaia and starry Ouranos,
he deceived the mind of Metis with guile
and coaxing words, and lodged her in his belly.
Such was their advice, so that of the immortals
none other than Zeus would hold kingly sway.
It was fated that Metis would bear keen-minded children,
first a gray-eyed daughter, Tritogeneia,
who in strength and wisdom would be her father's match,
and then a male child, high-mettled
and destined to rule over gods and men.
But Zeus lodged her in his belly before she did all this, that she might advise him in matters of good and bad."
After Zeus swallowed Metis, he gained some of her powers of wisdom. And since Metis was obviously pregnant with a daughter at the time, it also became the responsibility of Zeus to give birth to their child. Eventually, the wise goddess Athena emerged from her father's head and took her place among the exalted group of Greek deities known as the Olympians.
Who's Who in Classical Mythology