An opera showstopper is a popular ARIA, or solo song, from an opera that is so well-known and beloved that it stops the show. An ARIA is a self-contained piece of music written for a solo voice, usually with orchestral accompaniment. It is often used to express a character's emotions or to advance the plot of the opera. Opera showstoppers are usually performed at the end of the opera, and they often feature a powerful vocal performance.