In scenes 4 to 5 Macbeth soliloquy compares life to several things. they are life is.....

Well here is the part of the quote you want,

Life's but a walking shadow, a poor player,

That struts and frets his hour upon the stage,

And then is heard no more. It is a tale

Told by an idiot, full of sound and fury,

Signifying nothing.

Then he does his "out brief candle bit"

Really Macbeth is fed up with life. He says it is brief and meaningless.