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When Rob Lowe watched "Behind the Candelabra" for the first time, the actor found it so over-the-top that he couldn't believe it.

"I literally was thinking, 'What have I just witnessed?'" he said, laughing. "I don't think there's been a movie like this ever made. I really don't. It's a spectacle. It's unlike any movie."

The film is HBO's much-anticipated biopic of the legendary, flamboyant pianist, Liberace. Michael Douglas plays Liberace, and Matt Damon his much younger live-in lover, Scott Thorson. Lowe co-stars as Dr. Jack Startz, the pair's plastic surgeon.

Lowe described the Steven Soderbergh-directed project as being "so gay, it makes an average episode of 'Glee' look like 'The Expendables.'"

WATCH: 'Candelabra' Producer Gets Love Scene Approval from Damon's Mom

Speaking to ABC News' Cecilia Vega in an interview that aired on "Good Morning America Today," Lowe said of his co-stars: "When you see them having a love scene, you know that the spectacle of Jason Bourne getting it on with Gordon Gekko is pretty extraordinary."

Damon is known for his portrayal of the character Jason Bourne, a tough spy who goes on dangerous missions around the world. One of Douglas' most memorable roles was that of Gordon Gekko, the ruthless corporate raider from the movie "Wall Street."

Lowe said his co-stars often found it hard to "look at one another without laughing.

"It got to the point, with Matt in particular, when we did our scenes together where he just wouldn't look at me … he would literally just not be able to look at me," Lowe said.

Photos from the movie - showing the stars in sparkly costumes with elaborate makeup - have been making the rounds online and heightening anticipation for the film.

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In one scene, Lowe said, he and Damon had baby oil on their bodies while dressed in Speedos, and he claims to have felt a little competitive.

"You know, look - I love Matt. He's a great actor. It's all good. But the fact of the matter is we're both going to be in Speedos. You know, I'm a little competitive," he said, laughing. "So, the question is, is how do you kind of assess the competition?"

Lowe added that there was "a lot of side glancing" going on.

Lowe spent many hours in the makeup chair to transform himself into Startz.

"It hurt. I mean, it really did hurt," he said. "I had my eyebrows pulled up a lot … it's taped and pulled and you have to wear a wig and there are wires behind you."

"Beyond the Candelabra" debuts on HBO on May 26. The film ended up at HBO after several big movie studios passed on it.

Lowe said he's immensely proud to be a part of the project, and the early buzz for it is promising.

"It's a testament to how far we've come as a culture … people are much more comfortable living and being honest with who they are, which is great," he said.