Heroic couplet

A heroic couplet is a traditional form for English poetry, commonly used in epic and narrative poetry, and consisting of a rhyming pair of lines in iambic pentameter. Use of the heroic couplet was pioneered by Geoffrey Chaucer in the "Legend of Good Women" and the "Canterbury Tales", and generally considered to have been perfected by John Dryden and Alexander Pope in the Restoration Age and early 18th century respectively. 
Example.
A frequently-cited example illustrating the use of heroic couplets is this passage from "Cooper's Hill" by John Denham, part of his description of the Thames:
History.
The term "heroic couplet" is sometimes reserved for couplets that are largely "closed" and self-contained, as opposed to the enjambed couplets of poets like John Donne. The heroic couplet is often identified with the English Baroque works of John Dryden and Alexander Pope, who used the form for their translations of the epics of Virgil and Homer, respectively. Major poems in the closed couplet, apart from the works of Dryden and Pope, are Samuel Johnson's "The Vanity of Human Wishes", Oliver Goldsmith's "The Deserted Village", and John Keats's "Lamia". The form was immensely popular in the 18th century. The looser type of couplet, with occasional enjambment, was one of the standard verse forms in medieval narrative poetry, largely because of the influence of the Canterbury Tales.
Variations.
English heroic couplets, especially in Dryden and his followers, are sometimes varied by the use of the occasional alexandrine, or hexameter line, and triplet. Often these two variations are used together to heighten a climax. The breaking of the regular pattern of rhyming pentameter pairs brings about a sense of poetic closure. Here are two examples from Book IV of Dryden's translation of the "Aeneid".
Modern use.
Twentieth-century authors have occasionally made use of the heroic couplet, often as an allusion to the works of poets of previous centuries. An example of this is Vladimir Nabokov's novel "Pale Fire", the second section of which is a 999-line, 4-canto poem largely written in loose heroic couplets with frequent enjambment. Here is an example from the first canto: