The King of Israel, about whom we sing, “David, King of Israel, is eternally alive;” representing the fact that he was promised a dynasty of kingship over the Jewish People forever.
He had great courage, as he demonstrated when, as a shepherd, he killed a lion and a bear. And, when he visited his brothers in battle with the forces of Shaul against the Philistines and observed the mocking behavior and heard the taunts of the giant Galyat (Goliath) against the G-d and the People of Israel, he approached him unarmed except with his slingshot and killed him with one shot.
He is called the “Neim Z’mirot Yisrael,” the “sweet singer of Israel,” for several reasons:
his great skill in playing musical instruments
his ability to lift the depression of Shaul Ha-Melech (King Saul) with his playing
his authorship of the majority of the Book of “Tehilim”/Psalms. The “Tehilim” are Songs of Praise of G-d and expressions of human emotions of love, grief, fear and triumph over fear, despair and triumph over despair; these Songs created under the inspiration of “Ruach HaKodesh,” the Holy Spirit.
According to Jewish Tradition, the “Mashiach,” or Messiah will ultimately come from the descendants of David.