The significance of the Miller's Tale is to show people that it doesn't matter how well you know someone because everyone's intentions are unclear. For example even though John had been married to Alison and had trusted her with everything even his life, she still betrayed him in end because he was unable to see what he real intentions were which were to bounce back and forth from men playing them all in the process, and tearing them against each other. The type of irony within the tale is dramatic irony because there are two other guys trying to get with Alisoun and John has no clue what is going on.