Big robots, bigger explosions — biggest Wednesday movie opening in box-office history. "Transformers: Revenge Of The Fallen" powered its way to $55 million in domestic ticket sales on its first day in theaters, according to Variety.com.

That number outflanks by more than $10 million the previous Wednesday box-office champ, "Harry Potter and the Order of the Phoenix," which pulled in $44 million on its opening day in 2007.

Playing in 4,200 theaters, "Transformers" grossed $16 million during its midnight showings, also a record for a Wednesday opening and the third-best for any day of the week, behind "The Dark Knight" ($18.5 million, Friday) and "Star Wars: Episode III — Revenge of the Sith" ($16.9 million, Thursday).

"Transformers" has a distinct possibility of having the highest-grossing Wednesday-to-Sunday opening run ever, possibly besting "Spider-Man 2," which raked in $152.4 in 2004.

The first "Transformers," which debuted on a summer Tuesday in 2007, took in $124 million over a five-day period. The movie went on to gross $319 million at the box office. "The Dark Knight," which opened on a Friday, has the highest ever five-day debut, grossing $205 million, followed by the Thursday opening of "Revenge of the Sith" ($173 million).

Paramount, the studio behind "Transformers," will release its official numbers on Thursday.

This summer movie season has been somewhat slow compared with last year's, when films like "Indiana Jones and the Kingdom of the Crystal Skull," "Dark Knight" and "Iron Man" soared past the $300 million mark. The highest grossing summer '09 flick thus far is "Star Trek" ($241 million). After Sunday, however, "Transformers" should be well on its way to crossing the $300 million threshold.

Check out everything we've got on "Transformers: Revenge of the Fallen."

For breaking news, celebrity columns, humor and more — updated around the clock — visit MTVMoviesBlog.com.