King Saul was the first ever King of Israel. He was, of course, appointed by the Lord, but after many decades of rule, he had lost the Lord’s favour. God thus decided to afflict him with an evil spirit, as you do; and further, tipped off the prophet Samuel to this. As you do.
Samuel went to Saul, and told him that the solution to his problem is to be found with the sons of Jesse. As it turns out, David, the youngest son of Jesse, is able to play the lyre – and his lyre-playing eases Saul’s affliction. Lacking any surviving sons, Saul appoints David his heir. As you do.
Chapter Seventeen of the First Book of Samuel describes Goliath thusly:
And there went out a champion out of the camp of the Philistines, named Goli’ath, of Gath, whose height was six cubits and a span.
And he had a helmet of brass upon his head, and he was armed with a coat of mail; and the weight of the coat was five thousand shekels of brass.
And he had greaves of brass upon his legs, and a target of brass between his shoulders.
And the staff of his spear was like a weaver’s beam; and his spear’s head weighed six hundred shekels of iron: and one bearing a shield went before him.
6 Cubits and a span is 2.97 metres (or 9 foot 9 inches, if you prefer). Fortunately for the Israelites, it turns out that this Schwarzenegger of the ancient world has a glass jaw, or rather, a glass forehead. (And a suspiciously convenient gap in his helmet of brass.)
David, our Israelite hero, is able to slay the Phillistine man-mountain with a single well-cast stone, that cracks open his mighty head and kills him stone dead. David goes on to become King of all Israel; Goliath doesn’t go on at all.