Billie Eilish performs in Auckland as Laneway tease

The Laneway Festival line-up announced Monday is flush with international acts including 15-year-old American singer Billie Eilish.

She was in New Zealand for the announcement and performed in Auckland on Monday night.

The angelic looking pop star's lyrics aren't what you might expect - forget boy meets girl, teenage angst and heartbreak; this teen has a different take on music.

"That's [what other] people write about, that song already exists. Why not make something new?"

That's exactly what she did; her latest single 'Bellyache' is about being a serial killer. Eilish is trying to do away with pop star cliché's, and prefers to take on different characters.

"That's a fictional song, obviously. I don't kill people, but it's just fun to become someone that you will never be."

Eilish loves it when people go from just hearing her songs to really listening to them.

"A lot of people don't really listen to lyrics. Or they do, but they don't really process them. But that song ['Bellyache'] is like, if you listen you're like, 'woooo what is this person up to?'"

Eilish has been singing her whole life, but her big break came two years ago, when she was just 13.

"My dance teacher asked if I could make a song that he could use for one of the dances, and I thought that was the coolest thing ever."

So she went away and wrote a song with her older brother. The finished product was 'Ocean Eyes'.

The pair uploaded it to Soundcloud and, more than two million plays later, Eilish is now on Laneway's line-up.

"Literally, we put it up to send it to my dance teacher, just so he could have it."

'Ocean Eyes' has also hit more than 17 million plays on Spotify, and 'Bellyache' has 12 million.

Eilish's song 'Bored' was also used in the hit teen Netflix series 13 Reasons Why.

The teen says she's not into "fast fame" and is still figuring out what's next for her music.

Following her performance at Auckland's Tuning Fork on Monday night, she'll return to New Zealand to perform at St Jerome's Laneway Festival on January 29, 2018.

Newshub.