In William Shakespeare's Othello, the use of imagery and metaphors is significant in conveying meaning as it helps to establish the dramatic atmosphere of the play and reinforce the main themes. Through this, the audience is able to grasp a better understanding of the play.
Throughout Othello, images relating to poison frequently occur. These references are predominantly made by Iago. This seems appropriate for Iago who exhibits the characteristics of poison; they being fatal and deadly. There are several possible explanations to what motivates Iago: being overlooked for the lieutenancy, the belief that Othello and Cassio had committed adultery with his wife, though this is never really proved; class differences present in the society that made him feel inferior, and racial differences. This desire for revenge is so great it "doth, like a poisonous mineral, gnaw [his] inwards." Iago's use of language is a primary weapon in manipulating Othello.
By "pour[ing] this pestilence into his ear", Iago contaminates his thoughts. Once Othello starts to doubt Desdemona's fidelity, he is so incredibly driven by jealousy that it leads him to murder her, ironically with poison.