Donne expresses his metaphysical love. I would say he does so “forcefully” only in the sense that he does so with passion and confidence.
In the first stanza, the speaker speculates what he and the lady did before they met and fell in love. He concludes that any satisfied desire he experienced prior to their meeting was just a dream of what was to come with her.
If ever any beauty I did see,
Which I desir’d, and got, twas but a dream of thee.
In the second stanza, the speaker compares their relationship to a “little room” which is “an every where.” The world of their love is greater than what all explorers have seen.
Let sea-discoverers to new worlds have gone,
Let Maps to other, worlds on worlds have showne,
Let us possess one world, each hath one, and is one.
This is literally and figuratively metaphysical. Their love is Ideal and it is also beyond the bounds of materiality because it is greater than the larger expanses of the outside world.
In the third stanza, the speaker notes that their love is immortal. Again, this means beyond the physical (metaphysical). He expresses this in the Ideal sense of love as an abstract, eternal quality. But he also shows this by the metaphysical quality that emerges as a quality of their connection.
If our two loves be one, or, thou and I
Love so alike, that none doe slacken, none can die.
If two can be one, the idea of immortality seems hopeful. If two can be one, then maybe two can be infinite. As long as the love is perfect, it can escape the bounds of the physical world and the bounds of temporality.