The two appeared alongside each other in Battleship, a movie about fleet of ships that go to war with unknown creatures.
Liam is a fan of her music so he was excited to work with the singer.
"I was very pleased to meet Rihanna: I had already listened to all her songs and prayed that we would do a picture together," he told Italian magazine Grazia.
"At the end of shooting, if she asked me to jump into one of her video clips, I would say, 'Yes of course!'"
Liam was impressed with Rihanna's acting debut. He praised the Umbrella star's work on the film.
"Rihanna is a very talented person. One of those people who are able to do whatever they want with great results," he said.
While he admires Rihanna's ability to move from music to movies, Liam won't be following her footsteps as a singer. He is, however, pursuing a musical movie.
"I never thought about becoming a professional singer, but I am in touch with Bono [from U2] about releasing a musical movie," he revealed.
"It will be about an Irish band during the '70s who are looking for fortune in Las Vegas. I should play the singer of the band but I don't want to sing in front of anybody. So when nobody looks at me I'll start to sing."
But Liam refuses to direct a music video. He recalls once having a horrible experience when he was behind the scenes of a video clip.
"Some years ago I directed a video clip. It was the worst experience of my whole life," he said.
"I will never become a director or a movie producer. I was always looking at picture directing because I didn't know what to do! You can't be a movie director without real preparation. So, I made a mistake that day, and I will not repeat that experience."
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Working in isolation doesn't suit you. You're a social creature who gets your best ideas when collaborating with others. Unfortunately, that's not possible right now. Resign yourself to this difficult situation. If you do a good job, you'll pave the way for bigger and better assignments. Part of the problem is you lack experience. The only way to get the training you need is to do some volunteer work. Making a temporary sacrifice will eventually pay off. Be patient.More