I think a simple chart answers this best, so you can look at http://contenderministries.org/mormonism/comparison.php
Here are a couple of Mormon beliefs and their reference. I believe D&C is Doctrines and Covenant, not certain what book Mormon Doctrine is, but this could give at least a small sample of teachings the run smack against what mainstream Christianity teaches.
God the Father has a wife, through whom he procreates spirit children.
"Implicit in the Christian verity that all men are the spirit children
of an Eternal Father is the usually unspoken truth that they are also
the offspring of an Eternal Mother. An exalted and glorified Man of
Holiness (Moses 6:57) could not be a Father unless a Woman of like
glory, perfection, and holiness was associated with him as a Mother"
(Mormon Doctrine, 1977 ed., p. 516)
Man was also in the beginning with God. Intelligence, or the light of
truth, was not created or made, neither indeed can be" (D&C 93:29)
"If there had been no atonement, temporal death would have remained
forever, and there never would have remained forever, and there never
would have been a resurrection. The body would have remained forever
in the grave" (Mormon Doctrine, 1977 ed., p.63)
"Redemption from death, through the sufferings of Christ, is for all
men, both the righteous and the wicked" (Ibid., p. 65)