When Goliath saw David, he was furious because he wanted to fight the strongest Israelite and David was small and wimpy. David then explained he has God on his side who is much more powerful than Goliath is.
I may be small but I have God on my side and he is much more powerful than you!
Who is this man! I wanted to fight the strongest Israelite!
David took a stone, put it in his slingshot, and swung it at Goliath before he had a chance to use his sword.
David then went over to the fallen down Goliath, grabbed his sword and sliced off his head.
The Israelites started celebrating after the Philistines ran because they knew they had lost.
David then replaced Saul as the new king of the Israelites and followed God's commands as he was supposed to.