King David was the second King of Israel, the first being Saul. He was the youngest of eight sons of Jesse, but he was chosen to take over for Saul as king. David, being the youngest, was the shepherd for his father's sheep. He was anointed by the prophet Samuel.and also jesus is his descendant due to a promise god made to him.
His heroic role was in the story of David and Goliath, in which after healing king Saul with a harp, he was chosen to fight the Philistine giant Goliath. He did it with the power of God, and threw a stone at Goliath in the forehead with a sling, causing him to fall face-down, and then David used the giant's sword to cut off his head.