Since apparently most people didn't get a chance to read the poem, this became more about the way heroic couplets work, as opposed to Miltonic and Shakespearean blank verse. Basic idea: the severe constraints of the couplet require extreme push back from the poet in terms of balance, variation, surprise.  We talk about rhyming and look in some detail at one four line sequence from the start: 

Say what strange Motive, Goddess! cou'd compel
A well-bred Lord t'assault a gentle Belle?
Oh say what stranger Cause, yet unexplor'd,
Cou'd make a gentle Belle reject a Lord?
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