It's Avril Lavigne's birthday, and Mod Sun is celebrating with her.

Mod Sun, 34, wished his lover, 37, a happy birthday in a romantic Instagram post on Monday, referring to her as "the love of his life."

"Happy birthday to my soulmate, the love of my life, my favorite person in the world…..my angel. To the most radiant + graceful woman I've ever laid eyes on, you have made my dreams come true in so many ways," he captioned the post. "You are my calm in the chaos + my shelter from the storm. You are elegance + rock n roll wrapped up in one body."

"I was born without you, dying to find you, I'll always remind you….I love you with all my heart @avrillavigne+ the best is yet to come. Happy birthday my little icon," he continued.

Lavigne replied with an equally sweet post. "The sweetest most beautiful words ever. So glad I get to spend it with you my sunshine. 'I la la la la la la la la la love you',” she wrote.

Earlier this month, Lavigne expressed her support for her boyfriend ahead of his first gig on his Internet Killed the Rockstar tour. She penned a note for him, which she posted on Instagram along with a series of photographs of him and the band.

"Wishing my love @modsun and the boys a happy tour. Internet Killed the Rockstar Tour kicks off tonight. Some pics from last weekend," she captioned the post.

Mod Sun said, "F--- I love u so much. Thank u for everything babe. I can not wait for u to show the world what you've been working on. Ur an absolute icon + the most beautiful thing on this planet."

The duo also recently debuted on the red carpet at the MTV Video Music Awards in 2021.

The duo posed together and made a punk-style statement at the award event, with Lavigne wearing a hot-pink checkered suit and Mod Sun wearing a black suit with patches.

After being caught dining to dine together at the BOA Steakhouse in Los Angeles in February, the duo fueled dating speculations. A source told PEOPLE at the time that they had been in the studio almost every day for over two months working on Lavigne's new album, which is due out later this year.

The duo was seen on a double date with Megan Fox and Machine Gun Kelly in March. In January, Mod Sun gushed about Lavigne on Entertainment Tonight Canada.

"Avril Lavigne has one of my favorite voices in music," he said in a statement, according to the outlet. "It's so strong and confident, yet filled with emotion and one-of-a-kind inflections that only her voice can do. This song holds a lot more weight than meets the eye. There's a very deep message within it."