After the songs are sung and the votes start coming in, there is a 10 or so minute gap to fill in Eurovision. After that you go around to the various countries and tally up the votes and crown the winner! So the host country tries to choose an act that will wow the arena crowd and home viewers and keep the momentum high. Often they choose a local act with a great combination of talent and edge (or at the very least a lot of one or the other). Ireland, for example, debuted a showy troupe called Riverdance in 1994 that almost overshadowed the Contest itself.
Since the interval act can have all the elements that an actual entry only dreams of, like a massive orchestra, chorus, or dance troupe, huge special effects that spill out into the arena, and any combination of live and prerecorded music and vocals the heart can desire, it can and should be spectacular.
In 2007 Helsinki and Finland were hosting the contest for the first time, and wanted to show the world the kind of music Finns really like, dark, edgy rock! So they enlisted local ensemble Apocalyptica, a cello group with a twist–they were famous for performing their rock/classical take on the hits of Metallica. Their 2007 interval act combines music, art, performance, costume and special effects to showcase Finland as a center of new and creative entertainment!