Sappho is a famous Archaic period female poet from the island of Lesbos in the Aegean. Her sexuality is often the subject of debate among classicists. Early (pre-twentieth-century) translators completely ignored the feminine homoerotic sexuality, while nowadays Sappho is held up as a paragon of female homosexuality. The reason for her suspected homosexuality is the use of the Greek feminine pronoun ("she"/"her"). It is important to remember when discussing the historical Sappho that very little of her work survives. In fact, her poetry survive as papyrus fragments which bear only two complete poems.
Sappho's "Fragment 31" is the poem most often cited to evidence Sappho's homosexuality. The poem begins: "He seems to me equal in good fortune to whatever man who sits on the opposite side to you and listens nearby to your sweet replies." While the gender of the poem's addressee is ambiguous in the English, in the Greek text, the pronoun is feminine. Essentially (and by way of context), Sappho is expressing jealousy of a man who has earned the love of the (female) object of Sappho's own affections. This single fragment (coupled perhaps with Fragment 16, which is also her most metaphysical) has led Sappho to be championed as the famous lesbian poet. Fragment 16 discusses Helen's love for Paris and her role in the Trojan War.
As to your request for comparison with heteronormative/metaphysical poetry, John Donne is probably the most famous exemplar of this genre. John Donne's famous "Valediction Forbidding Morning" is, in some scholars' view, sexual in nature, though ostensibly about romantic love. In the interest of thoroughness, it is important to note that Sappho wrote about many subjects (including her family, specifically her own brothers, as evidenced in a recently discovered papyrus fragment). I would say that, if there were ever a precursor to metaphysical poetry, it would be from Archilochus, a Greek lyric poet from the island of Paros whose poetry is rife with sexual allusion.
Sappho is, unfortunately, too often interpreted in a hyper-sexualized way. While little is known about her, she is clearly a well-educated and artistic female, but her interests extend beyond sex to the realms of family life, beauty, and the definition of true love.