Chapter 16 ends with a sweet and bitter taste, David is chosen by God as the new king and Saul is rejected, but it is very interesting that David is brought to action precisely to comfort the afflicted king Saul(1 Samuel 16: 14-23.)
David had a lot of confidence in God, the same confidence that made him a good pastor will help him develop as a great leader of the people of God. When everybody was trembling because of Goliath he went ahead and defeated the giant.
Trusting in God has its consequences too. The powerful king Saul did not see David accomplishment as something to celebrate, but on the contrary to be aware of. The women of Israel were celebrating the victory of David over Goliath, and the victory of Israel over the Philistines with dance and Songs, but Saul was worried about the possibility of losing his kingdom.(1 Samuel 18: 6-16)
Now a beautiful friendship was developing between David and Jonathan. This friendship would be a providential one for David. Again Jonathan would demonstrate to have greater spirit than his father, even thought David is central in this narrative, I think Jonathan is a great example of character and devotion to God.
These days the Christian church needs great leaders like David, but also wonderful friends like Jonathan. Yes we need reliable people who are willing to take care of others even though it might represent a risk for them. Jonathan was willing to risk his own security just to bless his beloved friend David.
Saul on the contrary was willing to risk the whole kingdom to avoid the possibility of David becoming the next king. The saddest thing for me is that Saul has spent much of his energy trying to preserve something that God had already taken from him.