Replying to No Arguing Here...Just a question about Mormons

So, most people will tell you that to be a Christian, all you have to do is believe that Jesus died for you and accept him as your savior. (One could argue with this, try to change a few words and make it better, but let it go, it is no the point) My question is this- is there a fundamental belief that makes someone a Mormon, like one thing or a few things that you have to believe to be one besides the regular Christian thing?