They asked for a King to lead them into battle. King Saul was the tallest man around in Israel. However, their great and tall king is small compared to the giant Goliath. The people were trembling in fear because their leader was not able or unwilling to lead them into battle against the other side when they have a giant.
Who steps up to fight the battle. David who did not have his eyes on King Saul, but on God. Rather than seeing themselves as too small to win the battle David saw God as too big to lose the battle. He will fight Goliath in the name of the LORD and relying on the strength of the LORD.
Here is the question we must actually ask. Who really had the advantage in this fight? On paper it seems that David is the underdog. Undersized and no match for man like Goliath. However, two factors make me think maybe he should have been considered the favorite to win. 1.) The most important component is that David knew God was on his side and would give him the victory. The LORD will hand you over to me he says to Goliath. 2.) David fought from his strengths and didn't let the enemy dictate the battle. David did not fight the Giant in hand-to-hand combat. He fought him from a distance with the great precision he had with a sling and stone. David didn't let the enemy dictate how the battle was going to be fought. David fought on his terms and from his strength in reliance on God. In a similar we have an enemy that wants to us to rush into temptations and foolishness. Like David we must be aware of the battle and fight Satan on our terms not his. We must be wise to stand in our strengths rather than letting the Devil get a foot hold. We must rely on God for the victory.