Jesus Is the Father Because He Has Submitted Himself Completely to the Will of Heavenly Father and They Are of One Heart and Mind
Throughout Jesus' earthly ministry, He constantly submitted His will to the will of His Father: "I came down from heaven, not to do my own will, but the will of Him that sent me;" (John 6:38); "I can of mine own self do nothing: as I hear, I judge: and my judgment is just; because I seek not mine own will, but the will of the Father which hath sent me;" (John 5:30); "When ye have lifted up the Son of man, then shall ye know that I am he, and that I do nothing of myself; but as my Father hath taught me, I speak these things. And he that sent me is with me: the Father hath not left me alone; for I do always those things that please him." (John 8:28-29).
In that sense Jesus did not come to improve God’s view of man nearly so much as He came to improve man’s view of God and to plead with them to love their Heavenly Father as He has always and will always love them. The plan of God, the power of God, the holiness of God, yes, even the anger and the judgment of God they had occasion to understand. But the love of God, the profound depth of His devotion to His children, they still did not fully know—until Christ came.
So feeding the hungry, healing the sick, rebuking hypocrisy, pleading for faith—this was Christ showing us the way of the Father, He who is “merciful and gracious, slow to anger, long-suffering and full of goodness.” In His life and especially in His death, Christ was declaring, “This is God’s compassion I am showing you, as well as that of my own.” In the perfect Son’s manifestation of the perfect Father’s care, in Their mutual suffering and shared sorrow for the sins and heartaches of the rest of us, we see ultimate meaning in the declaration: “For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life. For God sent not his Son into the world to condemn the world; but that the world through him might be saved.”
Therefore, Jesus is the Father because His will has been swallowed up in the will of the Father. They possess the same attributes and characteristics perfectly. And the only real difference between Them is that They are separate personages.
Through Jesus Christ's Atoning Sacrifice, He Is the Father of All Those Who Repent and Receive Him
Jesus' transcendent Atonement not only united His will perfectly with the will of the Father, it also made Him the Father of all those who believe. Jesus taught, "Except a man be born again, he cannot see the kingdom of God." (John 3:3).
No child can be born without a father.
And now, because of the covenant which ye have made ye shall be called the children of Christ, his sons, and his daughters; for behold, this day he hath spiritually begotten you; for ye say that your hearts are changed through faith on his name; therefore, ye are born of him and have become his sons and his daughters.
And under this head ye are made free, and there is no other head whereby ye can be made free. There is no other name given whereby salvation cometh; therefore, I would that ye should take upon you the name of Christ, all you that have entered into the covenant with God that ye should be obedient unto the end of your lives.
And it shall come to pass that whosoever doeth this shall be found at the right hand of God, for he shall know the name by which he is called; for he shall be called by the name of Christ.
And now it shall come to pass, that whosoever shall not take upon him the name of Christ must be called by some other name; therefore, he findeth himself on the left hand of God.
While all men and women are spirit sons and daughters of Heavenly Father, Jesus Christ is the spiritual Father only of those who are born again. And unless Christ becomes our Father, we cannot be saved. We must literally take upon ourselves the name of Christ as His spiritually begotten sons and daughters.
Jesus Christ Is the Literal Son of God
Jesus Christ is the Only Begotten Son of God in the flesh. Mary was his earthly mother, but Joseph the Carpenter was not his father. In some miraculous way yet unknown to us, a Virgin conceived and brought forth a Son. (Isaiah 7:14). After all, the angels had good reason to sing that first Christmas night. In a vision explaining his father’s dream of the tree of life, Nephi saw the "most beautiful and fair [of] all virgins" holding the Son of God. (1 Nephi 11:15-22). Instantly, Nephi recognized that the tree of life symbolized Christ and knew that the baby born in Bethlehem was the embodiment of God’s love for His children; "For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life." (John 3:16).