The Lord has provided what we need to kill giants in our life, to endure persecution, to escape the bonds of hell. This quality can be anyone's. David represents the internal truth of the Word. This is a special gift that is given from the Lord as a result of His second coming and the opening of the spiritual sense of the Word. It is given in the degree that we desire to learn to serve the neighbor with genuine charity.
All kings mentioned in the Word represent the truth that rules our life.
Saul, the first king of Israel, represents the external or literal truth of the Word. If obeyed, it has a certain power to protect our spiritual life. It is a basis for an external order but no defense against the spirit of evil. The history of Israel shows that Saul had success against the enemies surrounding the land but was unable to conquer the Philistines in his midst. Saul had to be succeeded by another king who could deal with this more powerful enemy.