"Transformers: The Last Knight" will be set primarily in the modern day, with Optimus Prime heading to Cybertron and the other characters fighting the villains back on Earth. However, there will be scenes set back in the past, during the times of King Arthur, and a report has revealed that the studios are looking to cast Liam Garrigan as King Arthur.

According to a report from Mashable, Garrigan is currently in talks with Paramount to portray the iconic character. It is noted that this is not the first time that Garrigan portrayed King Arthur as he has played Arthur in the popular fantasy drama series, "Once Upon a Time" on ABC. 

The report further points out that despite both King Arthur and Merlin are going to apear it in the film it is unclear if they are going to be depicted as human beings or as Transformers. It would make sense for Arthur to be a Transformer given that he may have had the Matrix of Power at one time, proving himself as a worthy leader.

Fans also speculate that if Arthur and Merlin are Transformers then they may appear in the modern day, helping the modern Autobots in their battles against the Decepticons.

Garrigan is also known for his roles in "24: Live Another Day," "The Legend of Hercules" and "Strike Back."

Michael Bay will be returning to direct, making this his fifth film in the franchise to handle although the upcoming spin-offs will be helmed by other directors and writers. There will be a "Bumblebee" film as well as a sixth official entry in the series that will release by 2019.

It is unclear if "Transformers: The Last Knight," with its introduction of a wider universe of characters such as King Arthur, will be the starting point for the "Transformers" cinematic universe.

"Transformers: The Last Knight" will release in theaters on June 23, 2017.