Just thought I'd share this because I'm amazed at how many people know and love this movie but have missed the significance of it's beautiful metaphor.
Dorothy, Scarecrow, Tinman, Lion represent everyone of us with or thoughts of being incomplete, imperfect and needing something outside of ourselves for fulfillment. (Heart, courage, brain, being home)
Yellow Brick Road--path of life
Emerald City/ Wizard of Oz --hope in fulfillment of something in the future and outside of us (JW's New World)
Upon finding out the Wizard is a hoax --they discover they had everything they needed all along WITHIN them ("the Kingdom is in your midst)
They needed the journey along the road with the White Witch and Black Witch (good and evil, yin and yang) to create the obstacles and challenges needed to bring forth what was within them and discover their own greatness.
Dorothy realizing it was a dream, an illusion, and that she was in fact always at home no matter where she thought she was.
This is just an overview of the main theme but there's many more details involved. As with all metaphor or mythology have fun exploring!