(from a variety of sources)
Metaphysical poetry arose as a reaction to the extremes of Petrarchism; one problem with Petrarchan poems is a kind of predictability-the conceit is found, presented, & elaborated, but there are few subsequent surprises. Donne and his followers like to catch us off-guard, change direction, etc., to foil expectations. Metaphysical poetry is, in general, characterized by its ingenuity, intellectuality, and frequent obscurity.
In terms of subject matter, metaphysicals reject not only Petrarchan rhetoric but also the pose of abject worship of the mistress which sonneteers had inherited via Petrarch from the troubadours; in its place they put sexual realism and an interest in introspective psychological analysis of the emotions of love and religion (sometimes expressing the one in terms of the other, and sometimes actually being metaphysical in subject matter too). These poets showed a penchant for the novel and the shocking, and relished obscurity, rough verse, strained imagery, and at their best can be startlingly effective.
Donne set the pattern by writing in a diction & metre modelled on the rough give-and-take of actual speech, and usually organized his poems in the dramatic and rhetorical form of an urgent or heated argument (with reluctant mistress, intruding friend, God, Death, himself). Employed a subtle and often deliberately outrageous logic; realistic, ironic, and sometimes cynical in his treatment of the complexity of human motives, whether in matters of love or religion.
Reputation-decline in 18th-19th centuries during which time they were seen as interesting but perversely ingenious and obscure eccentrics.; big upsurge in the 20th due to the favourable press from the likes of T.S. Eliot and Dylan Thomas.
Metaphysical Conceit->a highly ingenious kind of conceit widely used by the metaphysical poets, who explored all areas of knowledge to find, in the startlingly esoteric or...