Rock!
Parody music
They sing like pop music, but they also sing rock with Rammestei, their current music is considered pop-electronic
cool music
they used to sing Latin Pop
Rockstar, by Nickleback
Rap
Reggae.
Pop
zac efron music
Louis Tomlinson and the rest of One Direction sing Pop music mostly.
I think it's because he doesn't want to be like other guy celebrities who always talk about girls and how much they love them and that they want them. I personally like how Nickleback never really talks about girls, he talks about the world and his friends. Kind of like Michael Jackson.
Reggae.