It's a fundamental building block in poetry, often used in:
* Iambic pentameter: A line with five iambs (10 syllables total), common in Shakespearean sonnets and other traditional English poetry. Example: "Shall I compare thee to a summer's day?"
* Iambic tetrameter: A line with four iambs (8 syllables total), found in poems like "The Raven" by Edgar Allan Poe.
The iamb's rhythm is often described as "da-DUM," creating a natural, conversational flow.