And the multitudes that went before, and that followed, cried, saying, Hosanna to the Son of David: Blessed is he that cometh in the name of the Lord; Hosanna in the highest. – Matthew 21:9
And when Jesus departed thence, two blind men followed him, crying, and saying, Thou Son of David, have mercy on us. – Matthew 9:27
Matthew, who is also called Levi, was a Jewish publican (Matthew 10:3). This means he collected taxes from his fellow Jews to pay to the Jewish and Roman governments. Publicans were hated even more than our modern IRS because they supplemented their income by charging too much and skimming the profits off the top. Basically, they profited by stealing from fellow Jews.
The Lord had need of Matthew in His service so He called him to be a disciple. The Pharisees, and others objected, but Jesus explains that Matthew was only a sinner but now he has been called to repentance (Matthew 9:13).
As seen in the scriptures quoted above, Matthew writes his gospel from the view of a Jew seeing Jesus as the fulfillment of Old Testament prophecies. He emphasizes that Jesus is the promised Messiah and King (Son of David).
The genealogy in Chapter one is the line of Joseph through King David, to Abraham. This is the “father’s” lineage, the royal bloodline, and the promise to Abraham the Jews would desire to see.
Wise men come and worship Him and He is seen commanding angels as the Captain of the hosts of heaven. His initial audience would have been his fellow Jews, whom he was attempting to convince that Jesus is the King for whom they were waiting.