One example of Marvell's metaphysical approach is "To His Coy Mistress". This poem expresses the metaphysical conceit which is an attitude that comes across through a debate or argument.
In this poem, Marvell is essentially coming onto a woman who has no speaking voice in the poem. He uses great hyperbole and a forward tone with the intention of getting this woman that he is interested in to stop playing hard-to-get. She has been coy, and he is trying to point out that there has been time enough for that game, and now it is time to engage in a highly physical relationship. Having been written in 1681, this is truly some forward and aggressive writing about love.
So how does this fit the metaphysical poet definition? As the great argument begins it's construction, Marvell presents the thesis in the first stanza that if there was time, he would
"Love you ten years before the Flood,
And you should, if you please, refuse
Till the conversion of the Jews."
Marvell is essentially say that their courtship could go on forever, if they only had the time.
But the next stanza, presents the antithesis: the fact that life is limited and they only have so much time to love.
"Thy beauty shall no more be found
Nor in thy marble vault shall sound
My echoing song; then worms shall try
That long preserved virginity,
And your quaint honor turned to dust,
And into ashes all my lust."
He is almost mocking her. He lets her know that she will die a virgin if she doesn't accept his request here pretty soon.
The final stanza marks the synthesis of the two ideas already presented. This stanza likewise makes the great suggestion that they take into account that time has been long enough for a flirting period, and now, it is time to let the sporting begin. Marvell wants to Mistress to understand that a physical relationship has to start at some point.
The structure of the argument is what defines this as metaphysical: thesis, antithesis, and then synthesis. Furthermore, the confidence in the argument that is marked by the hyperbole further defines this as metaphysical.
Hope this helps.