The phrase, “Son of God,” is a title of Jesus. It implies His deity (John 5:18) because the title is one of equality with God. In the Old Testament, it was figuratively applied to Israel (Exo. 4:22). In the New Testament, it is applied to Christ (Luke 1:35). It has many facets, for example: It shows that He is to be honored equally with the Father (John 5:22-23). That He is to be worshipped (Matt. 2:2, 11, 14:33, John 9:35-38, Heb. 1:6), called God (John 20:28, Col. 2:9, Heb. 1:8), prayed to (Acts 7:55-60, 1 Cor. 1:1-2).

See also What is meant when it says that Jesus is the Son of God?