Harry Styles slams Taylor Swift in the One Direction documentary film "This Is Us," but Styles may not be able to avoid backlash from Swift for long. Styles will have to face ex-girlfriend Taylor Swift at the Billboard Music Awards on May 19, which they will both attend.

In the One Direction documentary, Styles calls Swift a "pain in the a--." However, Swift has spoken out against Styles, as well. Last month, E! reported that Taylor Swift admitted that her hit song "I Knew You Were Trouble" was inspired by her relationship with the One Direction singer. Since then, a public 'battle' has ensued through the media, as the singers have taken shots at each other.

Harry Styles decided to talk about his failed relationship with Swift, which ended in January, in the documentary "This Is Us." Various UK tabloids reported earlier this week that he called his relationship a "huge pain in the a--."

Styles continued, "I think I've been unlucky in love so far but then, I haven't really met anyone who's made the earth move for me... I'm longing to meet someone who really inspires me and makes me really want to spend time with them."

But now, Styles will risk running into Swift at the Billboard Award ceremony in May, since both singers have been nominated for several awards each. This is the first time that they'll see each other since their breakup.

Taylor Swift will be performing at the Billboard Awards, and is actually competing against One Direction in two categories: Top Artist and Top Billboard 200 Album.

It'll be interesting to see if sparks fly between Styles and Swift at the Billboard Awards, but then again, there's a chance that the ex-couple will just ignore each other.

The One Direction documentary will be released in August. Although Styles ordered all footage with him and Swift cut from the film, viewers can look forward to gaining insight about Styles' public relationships with Caroline Flack and Cara Delevigne.