They are teens, so it's kind of funny to start with.
And they are kiwis. The video has subtitles for English speakers who can't understand the Kiwi accent (uh ... Americans?), so it's definitely funny.
And they are playing thrash-style heavy metal with lyrics in te reo Māori.
This is a documentary not a music video. Deep Māori culture background from around 12:00.
Anyway, once I've mastered Finnish maybe I'll learn Māori.