The stories in 1 & 2 Samuel are the stories of David.
The stories of David are stories of leadership.
They are stories of what a good king looks like. As a leader goes, so go her or his people.
They are stories that are a big, blinking neon sign pointing to the good shepherd king: Jesus.
In chapters 3, 4, and 5, the biblical writer shows the continuing story of David establishing himself as king in the land, which is no small feat.
First, David leads a national funeral for Abner.
While Abner served as the right-hand man to David’s lead competitor, David honors him as a hero of Israel, rather than a traitor. David knew who his true enemies were.
The good king shows his people how to grieve. (See John 11, Jesus and the death of Lazarus.)
Second, David punishes the assassins of his chief rival to the throne, the crown prince Ish-boseth.
David never at any time treats Saul, Saul’s family, or Saul’s supporters as enemies, even when they are trying to kill David. The enemies of David are the enemies of Israel—Philistines, Amalekites, Ammonites, and the rest. Saul represents something sacred and honorable to David. And this is a radically new idea in world where you can simply get rid of anybody that gets in your way.
The good king defies the accepted codes of culture and shows his people a new way. (See Matthew 5–7, Jesus and the Sermon on the Mount.)
Third, David captures the city of Jerusalem, taking it from the Jebusites, and establishes it as his base of operations.
To this point, there has been no capital city of Israel. It is here that David sets up a place of centralized government and worship for the country. From this point forward in the biblical story, this plot of ground becomes the most significant place in the world.
The good king redeems a place for his central activity. (See Acts 2, the day of Pentecost and the inception of the Church.)