Suttung was a full-blood giant who was the son of Gilling and his wife. He had at least one brother, named Baugi. He also had a daughter, Gunnlöd, who lived on his land in Jotunheim. To keep her safe from the affections of outsiders, he ordered her to stay put in one of his mountains, the Hnitbjorg mountain.
He took revenge on the dwarfs Fjalar and Galar for murdering his parents. Having cornered both of the dwarfs, Suttung claimed the Mead of Poetry in exchange for their lives. He stored the Mead in the Hnitbjorg mountain and blocked all entrances. This way, his two most prized possessions would be safe from the outside world.
Suttung had mastered shapeshifting. He transformed himself into a giant eagle when chasing Odin at some point. Surely he must have been a powerful giant, as Odin did not attempt to fight him.