I am sorry, melatonin doesn't really do anything. It might give some the extra "kick" to fall asleep in a relaxed situation at home, but it definitely is not useful for "I need to go asleep while being pretty wound up" which is what people are talking here.
One not-oft-mentioned thing melatonin seems to do (at least in my own experience) is that it cancels out the effects of earlier-consumed caffeine in preventing sleep. So if you're overtired and awake only because of caffeine, melatonin will put you out pretty quickly.
