This weekend presents the first real battle of heavy hitters at the box office. “World War Z,” Monsters University” and “Man of Steel” are all expected to do well, but which movie will come out on top?

The summer has already seen plenty of big releases including “Iron Man 3,” “Fast & Furious 6,” “Star Trek Into Darkness” and the big flop “After Earth,” but this is the first weekend where there is uncertainty at the top of the box office.

“Iron Man 3” had a week, and a massive debut, before facing “The Great Gatsby,” and, two weeks before, “Star Trek Into Darkness” was released, while the Memorial Day weekend saw “Fast 6” and “The Hangover Part III” battle. The end of May saw “After Earth” flop and last weekend saw “Man of Steel” debut with a $116 million take at the box office.

The next four weeks will be a very competitive time at the box office with the release of “World War Z,” “Monsters University,” “The Heat,” “White House Down,” “Despicable Me 2,” “The Lone Ranger,” “Grown Ups 2” and “Pacific Rim” among the big releases with several other big movies scheduled for late July. It remains unlikely any movie will beat the $1.2 billion “Iron Man 3” earned globally at the box office.

For the weekend’s new releases, “Monsters University” is expected to be crowned box office champion, Box Office Mojo reports. “Monsters University” has the luxury of being the first new family movie since the release of “Epic” over the Memorial Day weekend and opening in more than 4,000 theaters. Box Office Mojo estimates “Monsters University” to earn $73.9 million at the box office, while Variety believes the movie could earn up to $80 million. “Monsters University” should have some decent legs at the box office as it is a prequel to “Monsters Inc.” and has no competition until the release of “Despicable Me 2” on July 3.

The interesting battle is for second place between “Man of Steel and “World War Z.” The zombie movie starring Brad Pitt was in the news for all the wrong reasons due to a troubled production that led to plenty of reshoots. “World War Z” was not a cheap movie for Paramount, and a weak debut could lead the film to a similar fate as “After Earth” with Pitt joining fellow A-list celebrity Will Smith as a star of a summer flop.

Variety and Box Office Mojo expect “Man of Steel” to edge out “World War Z” for second place. Variety has a higher estimate than Box Office Mojo, an approximate $50 million take compared to $47 million, while Box Office Mojo is a little higher on “World War Z” than the industry.

“World War Z” could grab $40 million to $46 million at the box office. The estimated box office for “World War Z” does not spell doom as the film has been tracking well internationally and had impressive debuts in South Korea and Australia, the Hollywood Reporter notes.