Metaphysical poetry was popular around the same time as cavalier poetry. Where the cavalier poets wrote about love and parties and living lives of excess, the metaphysical poets were much more serious and particularly witty.
Metaphysical poetry was not popular at the time it was written, but enjoyed a strong following in the 20th Century with the help and admiration of T.S. Eliot.
Dryden and Dr. Samuel Johnson thought...
...that these writers were too concerned with showing how clever they were.
And whatever their motivation, metaphysical poets wrote very sophisticated material:
...[expressing] themselves in elaborate intellectualized images (often called "conceits").
Conceits were actually extended metaphors. Rather than simply comparing two dissimilar things, as was the case with a simple metaphor, a conceit would introduce an idea and then carry the comparison on—extending it beyond the initial comparison.
For example, one of John Donne's most famous conceits is a poem called "The Flea." Donne (during youthful years, before the serious years of religious dedication that would follow) wrote his poem to convince a woman to sleep with him. His argument was slightly convoluted...and certainly wove a flimsy and tenuous fiber of reasoning with which to convince her. In essence, he told the young lady that if they were both bitten by the same flea, their blood was mingled, making them intimately acquainted, so she should not resist going to his bed—for theirs would be like a marriage bed. (She did not agree.)
Metaphysical poetry allowed the author to write, and in selecting specific words, play word games with them in his poem.
The metaphysical poets wrote both love poems and religious or meditative lyrics.
In some of these poems, there was actually the "application of religious images and ideas to human love, and vice versa."
So metaphysical poetry was often written in the form of conceit: a fancy, clever extended metaphor in which the author plays games with words and means. They were sometimes love poems, or lyrics reflecting one's religious theology. Religious components were applied sometimes to "human love."