Macbeth talks about death as being the end of an unimportant life.
When Lady Macbeth dies, Macbeth has an interesting reaction. For the first time, he becomes philosophical as he ponders life and its end.
Out, out, brief candle!(25)
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. (Act 5, Scene 5)
As the enemy soldiers are closing in on him, Macbeth has to face his own mortality. His reaction to his wife’s death is his most poignant moment in many ways. He realizes that all of his struggles will end in death no matter what. She was his motivator, and he somehow lost sight of her once he became king. All he cared about once he got power was holding onto it.
Death is one of the major motifs in the play, and death's inevitability is an important theme. You can work to avoid it all you like, but in the end death is all there is.