Taylor Swift's adorable engagement party appearance

While many have dubbed her the queen of breakup songs, it was a collection of Taylor Swift's love songs that brought a US couple together in the lead up to their recent engagement.

Alex Goldschmidt's boyfriend Ross Girard is a total Swift superfan, so it's no surprise that her music has played a major role in their relationship, but Girard never could have expected what his partner had in store when they planned their engagement party.

Goldschmidt proposed to Girard earlier this month while hiking through the Hollywood Hills together, documenting the sweet moment on Instagram.

"Three years later, I proposed at the spot where I realized he was the one," Goldschmidt wrote, but the best was yet to come.

During the pair's engagement party Goldschmidt pulled his husband-to-be aside and addressed the crowd, revealing he had a surprise for them all.

"There is one secret that I didn't trust any of you with," Goldschmit told the crowd in a video he later shared to Instagram. "There was a person, who's not here, who sort of played a part in all of this."

Then in walks Taylor Swift, guitar in hand, as Girard and the guests gasped and celebrated.

"So Alex emailed me and said that he was going to do this and that there was a song that was very special to you two called ‘King of My Heart,'" she explained to Girard.

The song is said to be based on Swift's own relationship with boyfriend Joe Alwyn, the lyrics describing someone falling helplessly in love with someone after being hurt in the past.

"I’ve been off tour for a while, but hopefully it’s alright," Swift said before she sang, "This is from Alex, but sung by me."

Naturally the performance was flawless, Swift serenading the pair with nothing but her guitar and incredible voice, Goldschmidt sharing another video of the performance to his Instagram.

"You are the one I have been waiting for, king of my heart, body and soul," Swift sang while the loved-up couple watched on, the song holding a special meaning for the pair.

"I decided to propose to Ross listening to this song in my car," Goldschmidt captioned the sweet video.

It's not the first time Swift has gotten involved in her fans' love lives, with several couples getting engaged at her concerts, but this is the first time she's done such a special performance for a couple, and we're sure there are plenty of jealous Swift fans wishing they'd had the idea first.