I come to you in the name of the Lord - 1 Samuel 17:45
David spoke words of confidence
He knew that God had sent him and He never sends a man to fight without equipping and guilding him
Goliath had size, armor, weapons and a hard heart on his side
David had a slingshot, some stones, and an abolute faith in God (delights in enabling the impossible)
It was a hopeless situation - for the Giant
The moment David accepted God's call to fight, Goliath was as good as dead.
This is the Lords battle! - 1 Samuel 17:47
What "giants" in your life make you feel like the underdog? In Christ, can not only win over the giants but have an abolute rout.