As always, Shakespeare makes use of a good deal of blank verse, which is to say unrhymed iambic pentameter. The verses in the caskets and the comments of Morocco and Aragon thereon are in trochaic tetrameter, without the weak beat of the last trochee, as Dum-da Dum-da Dum-da Dum. The rhythm of "Tell me where is fancy bred" is similar: it may be scanned as iambic tetrameter as well as trochaic.
