Massive means enormous. Obviously, Mt. Everest is massive, but a massive budget cut isn't necessarily big in physical mass; it's something that is imposing in scale or power. A massive budget cut can do a lot of damage.
Unless someone is referring to your intellect, massive is not a word you want used in a description of your attributes. Massive is a nice one to trot out when huge, gigantic, and enormous sound too over-the-top. Politicians use it often. Massive could also be the best way to describe the wave you surfed on your Hawaiian vacation or the size of the fish you nearly caught on that trip with your friends.