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.