The Gospel according to St. Matthew is not a text simply stringing together haphazard events and occasions that present Jesus teaching valuable and true things. Beyond this, the Gospel text portrays the unity of Jesus' whole life. Very likely the earliest nucleus of the Gospel text is what is now its conclusion, that is, the narrative of Jesus' Passion, death, and Resurrection, which narrative no doubt constituted the heart and substance of the primitive oral kerygma, or "proclamation" of the faith by the apostles and their successors. Everything else in the Gospel text came later, composed to show how everything in Jesus' life and teaching eventually had to lead to his atoning death out of love.
In Matthew's Gospel we see how, against all obstacles and opposition, Jesus moves with a sovereign sweep from the promises of God in the Old Testament, fulfilling them in his Incarnation as Messiah, to his identity as a man who does divine things and speaks divine words (parables, miracles, encounters, discourses), to the culmination of the story in his Passion, death, and Resurrection, and, finally, to the conclusion of the story in Jesus commissioning the apostles to do what they have seen him do and teach what they have seen him teach. In the end, they are to become what they have seen him be.
Thus, the main message of Matthew's Gospel is that we are not saved by detached "doctrines" or "truths", but by the whole life of this man, Jesus of Nazareth, in all its fullness and unity. All Christian theology is but a systematic reflection on this life, on everything it reveals about God and us and on everything this revelation implies for our own future life and behavior.
In the Gospel, Jesus Christ the person and his action in our lives have absolute primacy over anyone's teaching about Jesus Christ.
Read more from the Introduction to Fire of Mercy, Heart of the Word (Vol. II): Meditations on the Gospel According to St. Matthew, by Erasmo Leiva-Merikakis: