I'm a fan (and you should be too) because...
Adam's the only real performer I have ever come across. The clarity and power of his voice is stunning; he doesn't just sing the songs, he feels each and every word of it. He has this ability to make all songs his own, a quality that filters out the artists from the singers.
He's an artist in the truest sense of the word. Its not just his voice that pierces into the heart; each and every one of his stage performances linger on and just refuse to leave...not that I mind.
When performing on the stage, its not just about the voice, its also about the appearance and the ability to rock the stage. Though many don't realize it, its not even half as easy as it sounds. The ease with which he acheives all this and more makes him a true performer.