The songs in this genre can be dramatically different, depending on the show they're from and what the circumstance is. As they're used to convey scene/events/emotion, there is a strong emphasis on lyrics.
The genre can be traced right back to ancient Greece, where performances included both music and dance. Now, there are many, many musicals in all sorts of forms!
The musical genre has recently risen to fame through programs such as 'Can You Solve A Problem Like Maria?' and 'Over The Rainbow', which are search for a star type TV shows where the winner gets to appear in the corresponding stage show. These tend to feature a combination of songs from different shows as well as different genres of music.
In the same vein, the song 'I Dreamed A Dream' became very, very popular after it was covered by Susan Boyle on Britain's Got Talent. Though initially laughed at by judges and viewers alike for her appearance, she wowed everyone with her voice. That's a bit irrelevant though.
Many musicals start as stage shows and are made into films, as seen recently in the massively popular Les Miserables.
I used to be really really into this genre; however, though there are still songs I really like, things have changed! The songs were hard to pick, because I have good memories associated with many of them. In the end, I mainly did it randomly!
If I Can't Love Her- Beauty And The Beast
As Long As He Needs Me- Oliver
One Day More- Les Mis
Don't Rain On My Parade- Funny Girl
One Night In Bangkok- Chess