We mentioned it earlier, but we'll give you the lowdown now. "On Being Brought" is written in heroic couplets. They were the in-thing for all the poets back in Wheatley's day.
Basically, she rhymed, she wrote in iambic pentameter, and her poetic style was all about reason, form, and restraint. She wasn't a romantic poet, using all sorts of flowery language and overblown emotions. She stayed cool, used reason, and never colored outside of the formal lines.
That's because she probably wanted to imitate the neo-classical greats, like Alexander Pope. Her virtuosic handling of formal poetry would earn her some serious street cred from the educated white audience and help establish her as a serious poetic talent. It was no small thing for a slave to be publishing poems. Writing formal verse like this was like saying, "See, I've got what it takes, just like the white guys that came before me."
So, let's get down and dirty about the meter with the first two lines (the bold are the accented syllables):
'Twas mer cy brought me from my Pa gan land,
Taught my be nigh ted soul to un der stand
These lines are in perfect iambic pentameter, and they rhyme. Those are the two ingredients we need to whip up a batch of heroic couplets, and Wheatley's laying 'em down like hot cakes here (okay, we'll stop right there with the baking analogy, but really, her lines are perfect).
But the question about form and meter is always why did the poet choose this particular form? Why not free verse? Or a sonnet? Anyone for quatrains?
Like we said, heroic couplets were all the rage back in Wheatley's time. They may have been a reaction to romanticism, but they're also what Wheatley knew. She was formally educated and could read and write Latin and Greek. The neoclassical poets often imitated the works of classic literature from the Greeks and Romans.
Wheatley makes an argument throughout her poem that she's been saved by the mercy of the Christian God and that, if she can be saved, then all Christians can be saved. That means, slave or free, black or white, they're all equal on the "angelic train."
Her argument, expressed in the rhymed couplets of her form, uses logic and a fixed rhythm that imitates the balance of her thinking and her message. The straightforward progression of iambic lines, the end rhymes, and the clear, logical thinking are classic neo-classicism. Really, the form is the message, and Wheatley's message is that she was saved by being brought, educated, and converted in a new country. Her virtuosic handling of heroic couplets reflects her new thinking.