After learning about his wife's death in act 5, scene 5, Macbeth elaborates and laments on life's meaningless nature by comparing one's existence to a brief candle, a walking shadow, a poor player, and a tale told by an idiot in his famous speech. Each of Macbeth's metaphors for life signifies its fleeting nature, lack of substance, and meaninglessness.
By comparing life to a brief candle, Macbeth emphasizes the ephemeral, temporary span of life. His words conjure images of wax slowly melting as a candle burns, which is how he views life at this stage of the play. Macbeth's metaphor comparing life to a walking shadow also underscores its lack of substance. The last two metaphors comparing life to a poor player and a tale told by an idiot highlight life's meaningless, absurd nature.
Macbeth's four metaphors reveal his loss of hope and negative outlook on life in his final days. He has completely transitioned into a callous, bloodthirsty tyrant who is full of regret, grief, and anguish. Macbeth clearly does not value life and his famous soliloquy reveals his negative perspective.