The lead sound in any track is by far one of the most important elements. It's what the listener will remember and, if executed correctly, they'll be humming the lead of the tune to themselves after the track is played.
Of course the notes you play in the lead, and how they combine harmonically, is of the upmost importance for the overall success of the lead sound.
What's often overlooked is the actual sound design of the lead. In this screencast, I'll show you how to create a three dimensional lead sound in Ableton 10 so the track will have the biggest emotional impact possible.