In 1887, the theatre reopened as a popular music hall named the Empire Theatre of Varieties, and in 1896, we are told that it hosted Britain's first commercial theatrical performances of a projected film, by Auguste and Louis Lumière. This theatre is also credited with having been the birthplace of the vacuum cleaner, after the inventor H. Cecil Booth visited to see the demonstration of a similar, but useless, machine which gave him the inspiration for his invention.
In 1927, Metro-Goldwyn-Mayer demolished the original theatre and rebuilt it as a cinema, which opened in 1928. The Empire still retains that 1928 façade, and though it stood hidden for many years after a 1960s refurbishment, it is open to the air today.
For more, see http://en.wikipedia.org/wiki/Empire,_Leicester_Square