When Laban asked his nephew what his wages shall be, Jacob pledged that he would work for him for seven years in exchange for marrying his youngest daughter Rachel. Laban agreed to the pledge and so Jacob worked to keep his flocks. By the time the seven years were finished, Laban gave Jacob a feast, but substituted Leah for Rachel. When Jacob realized his uncle cheated him by giving him Leah instead of Rachel, Laban made an excuse that it's not customary among his people to give the youngest daughter ahead of the oldest one and so had Jacob work for him another seven years in order to have Rachel.
During those years with Laban, God saw that Leah was "hated" by her husband because he loved Rachel more than her, and so enabled her to have children, whereas Rachel was left barren. Her first four children were Reuben, Simeon, Levi, and Judah. When she stopped bearing and Rachel was jealous of her sister having children, she gave her handmaid Bilhah to Jacob as a wife and she bore to him Dan and Naphtali. Leah responded by giving her handmaid Zilpah as a wife when she couldn't bear children, and so had through her Gad and Asher. Later on, Leah had Jacob sleep with her in exchange for giving some of her son Reuben's mandrakes to Rachel, and God enabled her to have children again: this time two sons Issachar and Zebulun and a daughter named Dinah.
Some years later, after Jacob had acquired a great deal of flocks from his uncle Laban's, Jacob was called by God to return to his own people and so had his wives and his children leave secretly without telling Laban. He soon found out and pursued after them, stopping at the mountain of Gilead to confront his nephew for taking his daughters away like captives and for stealing his household gods (which Rachel did behind Jacob's back). After unsuccessfully trying to find his stolen gods, Laban and Jacob made an agreement with each other and parted ways after saying goodbye.
Leah outlived her sister Rachel, who died while she was giving birth to her second son Benjamin. She was buried in the cave at Machpelah along with Abraham and Sarah, Isaac and Rebekah, and later her husband Jacob.
Leah is an ancestress of King David, and ultimately Jesus Christ, through her son Judah.