1. Metaphysical Poetry: The body of poetry produced by a group of seventeenth-century English writers called the "Metaphysical Poets." The group includes John Donne and Andrew Marvell. The Metaphysical Poets made use of everyday speech, intellectual analysis, and unique imagery. They aimed to portray the ordinary conflicts and contradictions of life. Their poems often took the form of an argument, and many of them emphasize physical and religious love as well as the fleeting nature of life. Elaborate conceits are typical in metaphysical poetry. Marvell's "To His Coy Mistress" is a well-known example of a metaphysical poem.
2. An early seventeenth-century (mostly Caroline) movement, centered on Robert Herrick, Thomas Carew, John Suckling, Richard Lovelace, and Henry Vaughn. Most were admirers of Ben Jonson. They get their name from the supporters of King Charles I in the seventeenth century: the Cavaliers were Royalists during the Civil Wars. (The supporters of Parliament were nicknamed Roundheads.)
It's traditional to oppose the Cavalier poets to the Metaphysical poets, including John Donne and George Herbert. Whereas the Metaphysical poets were fond of abstruse imagery and complicated metaphors, the Cavaliers preferred more straightforward expression. They valued elegance, and were part of a refined, courtly culture, but their poetry is often frankly erotic. Their strength was the short lyric poem, and a favorite theme was carpe diem, "seize the day."
Here's a famous, and perhaps typical, Cavalier lyric, Robert Herrick's "To the Virgins, to Make Much of Time":