How are iambs structured in English poetry?

In English poetry, an iamb is a metrical foot structured as a sequence of two syllables: one unstressed syllable followed by one stressed syllable. This pattern is often represented as an unstressed-stressed beat, similar to the rhythm of a human heartbeat.123

Because this structure aligns well with the natural cadence of the English language, iambic rhythms have become the preeminent metre in English verse. Poets build lines of varying lengths by repeating this foot, such as in iambic tetrameter (four feet) or the widely used iambic pentameter (five feet). While a poem may be fundamentally iambic, poets frequently substitute other types of feet into the line to add rhythmic variety.13