The Mormon Bible teaches God manifests himself in different modes
Does the Book of Mormon teach a Trinitarian concept of God? Some have assumed so because certain verses taken separately do seem to use Trinitarian language. However, taken as a whole, the Book of Mormon lends itself more to a modalistic understanding of God rather than Trinitarian. Modalism is an old heresy that attempts to defend monotheism, but does so at the expense of “confounding the persons” within the godhead. Modalists claim that God manifests himself in different modes. For example, God is revealed as Father in creation, Son in redemption, and Holy Spirit as the giver of grace.
Christianity affirms that there is one true and living God while also affirming that this one God exists eternally in three Persons — the Father, Son, and Holy Spirit. The Father is not the Son. The Son is not the Holy Spirit, nor is the Holy Spirit the same person as the Father. All possess the same divine nature but they do not represent three separate Gods.
There is no evidence to suggest that Joseph Smith was ever partial to the Trinitarian view of God. In fact, in his June 16, 1844 Sermon in the Grove, Smith likened the “three in one” God to a “giant or a monster” (Teachings of the Prophet Joseph Smith, p.372).
Examples in the Book of Mormon that tend to describe God in a modalistic manner include the following:
Mosiah 15:1-4 — “And now Abinadi said unto them: I would that ye should understand that God himself shall come down among the children of men, and shall redeem his people. And because he dwelleth in flesh he shall be called the Son of God, and having subjected the flesh to the will of the Father, being the Father and the Son — The Father, because he was conceived by the power of God; and the Son, because of the flesh; thus becoming the Father and Son — And they are one God, yea, the very Eternal Father of heaven and of earth.”
Mosiah 16:15 — “Teach them that redemption cometh through Christ the Lord, who is the very Eternal Father. Amen.”
Alma 11:38-40 — “Now Zeezrom saith again unto him: Is the Son of God the very Eternal Father? And Amulek said unto him: Yea, he is the very Eternal Father of heaven and of earth, and all things which in them are; he is the beginning and the end, the first and the last; and he shall come into the world to redeem his people; and he shall take upon him the transgressions of those who believe on his name; and these are they that have eternal life, and salvation cometh unto none else.”
3 Nephi 1:14 — “Behold, I come unto my own, to fulfill all things which I have made known unto the children of men from the foundation of the world, and to do the will, both of the Father and of the Son—of the Father because of me, and of the Son because of my flesh.”
Mormon 9:12 — “Behold, he created Adam, and by Adam came the fall of man. And because of the fall of man came Jesus Christ, even the Father and the Son; and because of Jesus Christ came the redemption of man.”
Ether 3:14 — “Behold, I am he who was prepared from the foundation of the world to redeem my people. Behold I am Jesus Christ. I am the Father and the Son. In me shall all mankind have light, and that eternally, even they who shall believe on my name; and they shall become my sons and my daughters.”
Ether 4:8, 12 — “And he that will contend against the word of the Lord, let him be accursed; and he that shall deny these things, let him be accursed; for unto them will I show no greater things, saith Jesus Christ; for I am he who speaketh. . .For behold, I am the Father, I am the light, and the life, and the truth of the world.
Ironically, modern Mormonism holds to a view of God more in line with tritheism, which recognizes the Father, Son, and Holy Spirit, but sees them as three distinct Gods within the godhead. Tritheism is not monotheistic and has never been an accepted Christian teaching.