When butterflies land on humans, they are often drawn by smell, either of perfume or perspiration. Since butterflies taste with their legs, the best way to inspect a sweet-smelling prospect is to land on it.
If a butterfly should land on you, it's best to not touch them, if possible. They will fly away of their own accord.
Watch and listen to Ota's lovely butterfly performance below:
(YouTube: Kanal tilhørende Odensesymfoni)