Standing Under Spotlight

I can be a shadow on anyone's wall.
But I can not do that,
Reflecting my own light.

I can cast a shadow at noon...
To have others believe,
I have energy to give I don't need.

But to leave to cast no shadow at all,
I am not yet prepared to do.
So...
If I am caught,
Standing under spotlight...
Bright with a smile toothy white,
You know the applause I am waiting for...
Is anticipated to come from you!