"Are Mormons Christian?"
This answer comes down to how the word "Christian" is being defined. I'll go over a few definitions and the resulting answers.
"Christian" = a person whom has faith in Christ. And that's it. Then yes, Mormons are Christian- Jesus Christ is my Lord and Savior. That's the definition I + other LDS Christians + many other Christians use: acknowledging and celebrating the foundational Christians relationships of Pentecostals, Baptists, Methodists, Catholics, Orthodox, etc. We don't have to agree on all theology to celebrate another's love of Christ.
"Christian" = a person whom has faith in Christ + passes these certain theological tests that I have decided are important. Depends on the added theological test. Spoiler alert: LDS Christians aren't Protestant, so if that's required the "no" is the answer. LDS Christians also don't subscribe to the post-Biblical Creeds (most notably the Athanasian Creed), so if that's required the answer is again "no".
If you want to give me your specific definition you're using
@Paul Christensen , I can go into that specifics.