Are Mormons Christians? No. Do they worship the same Jesus as we do? No.
See for yourself. These are short clips explaining Mormon beliefs. They come from Wretched Radio via LHVM.org, a website dedicated to explaining Mormon beliefs in comparison to the Holy Bible.
History according to Mormonism has no validation in any historical account, any archaeology, or any anthropological source.
How many wives did Mormon founders and leaders have, anyway? LOTS.
Though they downplay the polygamy issue, their religion does still teach you have to have multiple wives to become a god.
There is more at the Wretched Network. Get familiar with Mormonism. We will have a lot of witnessing to do. Even worse, Billy Graham confused the issue after he met with Presidential candidate and Mormon Mitt Romney and subsequently removed Mormonism as a cult listing from his website. Woe to Graham!
Anyway, these are short and concise clips.
Here is a good essay answering the question, “Witnessing to Mormons, what is the key?“
One key for all sanctified work is prayer. Keep praying for the Mormons who are oppressed in this cult, in darkness and not believing the true Gospel.