Luke:
It's passion. He knows that his career doesn't let him have that much time with you and he makes sure he can make every moment count.
Calum:
It's playful. He likes to kiss you whenever, wherever. He's definatly not afraid of PDA. It's usually unexpected but you end up smiling everytime.
Micheal-
It's aggressive. Tour keeps him away and everytime he talks to you it's always over Skype or FaceTime. Any physical contact he never takes for granted.
Ashton-
It's possessive. He hates when other guys flirt with you. His kisses are to show that you're his and for everyone else to give up. He doesn't like the idea of sharing.