"Most people think it's just a fast rock ‘n' roll song ... says this 1965 single from "Rubber Soul" is of the greatest songs ever written. Lennon even says that it was: "my first real, major ...

These classic rock songs almost went to completely different artists. One can't help but wonder if they still would have been hits.

But have you ever wondered why this six-minute single that no one ever thought would be a hit became one of the most famous songs ever written ... an opera or rock. It's actually all of them ...

Elton John credited Metallica as having one of the "best songs ever written," comparing it to the folk classic, "Greensleeves ...