The 39-year-old 'Magic Mike' actor will play supervillain Deathstroke in the upcoming standalone Dark Knight blockbuster, tentatively titled 'The Batman', which will star Ben Affleck as The Caped Crusader and is also being written and directed by the Oscar winner.
Before accepting the part of the DC Comics menace, Manganiello met with Affleck to discuss his vision for the film and was impressed with his plans for a "fresh take" on the Gotham City saviour.
Speaking on Mark Madden's Pittsburgh sports podcast, he revealed: "When I met Ben we sat down and we talked about, you know, the role. We talked about the movie. His take is a fresh take but I think the audience is going to be surprised.
Because it's a road that no one's really gone down that's completely integral to who Batman is. And I think it's gonna be refreshing but at the same time completely familiar. But it's going to take this franchise in a direction that I think a lot of people are going to be really happy about."
Manganiello - who has appeared in a Marvel comic book movie before, playing Flash Thompson in 'Spider-Man' - also teased that the blockbuster has a "gritty" plot which has already been fully fleshed out by Affleck, who has already donned the cape and cowl for 'Batman v Superman: Dawn of Justice' and had a cameo in 'Suicide Squad'.
He said: "It's going to be gritty and action packed and cerebral and all of those elements that people love about Batman. I told him in the room man, when I met him, 'I should be so lucky, I'd be in great hands to work with you, I love your movies, let's do this.' "
'The Batman' - the latest confirmed project in the DC Extended Universe from Warner Bros. Pictures and DC Entertainment - is expected to be released in 2018.
Affleck will next be seen as Batman in ensemble superhero movie 'Justice League' in which he stars with Gal Gadot as Wonder Woman, Henry Cavill as Superman, Jason Momoa as Aquaman, Ezra Miller as The Flash and Ray Fisher as Cyborg.