Who are they?
The easiest way to describe 5 Seconds of Summer is that they are the Australian "alternative" version of One Direction. The boys play their own instruments, wear skintight jeans, and have piercings, and at least one of them has colorfully dyed hair. However, despite their punkish look, their sound is unmistakably pop. Their lyrics are uplifting, supportive, and focused on romance — it's very clear that these guys are marketing themselves toward teen girls despite the fact that they don't want to be seen as a "boy band" and think of themselves as a rock-pop band. However, this group makes previous rock-pop bands (and their admitted influences) like Sum 41, Fall Out Boy, and Good Charlotte look like hardcore punks in comparison, but that is totally OK.
The video for their first single, "She Looks So Perfect," is really the best introduction to the group. Watch it above.