If you're a Paramore fan, you may think that you know exactly what to expect from the debut solo single by Hayley Williams.

The rock/pop-punk band had a pretty distinct style and image, mostly thanks to their frontwoman.

Nevertheless, many people have been surprised by her first solo single 'Simmer', which has what some people are calling a more 'mature' sound.

There's no doubt about it, it's a pretty good song.

It's the first song from Williams' forthcoming debut album, 'Petals for Armor', which is out on May 8th.

"I’m so ready and so incredibly humbled to get to share this project," she said. "Making it was a scary, empowering experience. Some of my proudest moments as a lyricist happened while writing PETALS FOR ARMOR. And I was able to get my hands a little dirtier than usual when it came to instrumentation.

"I’m in a band with my favorite musicians so I never really feel the need to step into a role as a player when it comes to Paramore records."

See the social media reaction to 'Simmer' below: