He is identified in the Amarna letters as a son of Labaya, the ruler of the hill country north of Jerusalem, including the territory in the vicinity of the city of Shachmu (biblical Shechem).
After his father's death at the hands of the citizens of Gina, Mutbaal and his brother continued their assaults on other Canaanite rulers and their holdings, employing Habiru mercenaries.
[1] EA 256 is about Mutbaal, and Pella-(Pihilu); a list of cities in the letter, in the Golan Heights=(Garu)—Udumu, Aduru, Araru, Mešta-(Meshta), Magdalu, Heni-anabi-(Kheni-anabi), Sarqu, Hayyunu, and Yabiluma.
People mentioned in this letter include Dadua, Yishuya and Ayab, whom Rohl identifies with David, Jesse, and Joab.
David Rohl identifies Mutbaal with Ishbaal or Ish-bosheth, the son of the Israelite King Saul, but the chronology that would make this identification feasible is not accepted by the majority of scholars.