Avril Lavigne and her fiancé, Nickelback frontman Chad Kroeger, joined host Ryan Seacrest on his radio show Tuesday and debuted the first single for her forthcoming album, Here's To Never Growing Up.

In the On The Air With Ryan Seacrest interview, Kroeger, 38, shared how he fell for the 28-year-old singer.

"I think it evolved into this wonderful thing," Kroeger told Seacrest. "When you're sitting there, singing across from somebody into the microphone and singing love songs and you start developing these feelings for that person, and it just blossomed into this thing and last summer we started dating and I didn't take long, I got down on one knee."

Lavigne also shared her side of the story of how the couple got engaged last summer only a month after dating. She revealed the details of his proposal and described it as "romantic."

"The only thing that was weird was we usually go to the studio together and he had gone before me," Lavigne said. "And I have been making this scrapbook of my time in the studio with a Polaroid camera and the only thing that was weird was I walked into the studio and he was putting a picture into the book and I was like 'What is he doing?'...And all of a sudden I walk over and he had taken a photo of himself holding the ring box and put the Polaroid in my scrapbook and because I had stickers everywhere he put in 'Will you marry me?' It was really romantic."

Seacrest asked the couple about their wedding plans, namely if they had selected a theme yet. Lavigne said it will be "quite spectacular" and that it will be "pretty big" and that her husband-to-be didn't know any of the plans for their nuptials yet.

"I can't tell you that but we're planning it." Chad added, "everyman knows we get very little participation in the wedding and these are goods things or else Steel Panther ends up playing."

Seacrest asked Lavigne to describe her new single before he played it for her fans to hear for the first time. She described it as a "pop rock tune."

"It's just about being young, having fun, being present, living in the moment; and that's what I love to do," she said.

Listen to Avril Lavigne's new single Here's To Never Growing Up here.

Lavigne's fans can download Here's To Never Growing Up on iTunes here

Watch Avril Lavigne and Chad Kroeger's interview with Ryan Seacrest below.

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Avril Lavigne, Chad kroeger