One of the more memorable sequences in Luc Besson's The Fifth Element is the concert sequence featuring Diva Plavalaguna, played by Maïwenn Besco. In the original movie the song plays, but there are plenty of cuts between the stage and other characters, so you never get to see the full song.
Luckily the footage of Maïwenn Besco doing the full performance against a green screen is online and it's fantastic.
Here it is:
And here's the version you're used to seeing in the movie with all the cuts:
The song, in case you're interested, is "Il Dolce Suono" by Gaetano Donizetti