There's almost something Jaws-like about reading "The Raven" out loud. Go now and do it. I'll wait.
First, Poe uses trochaic meter. That's not the dumDUM iamb we all loved so dearly in high school, but the DUMdum trochee nobody ever told us about. Then, he puts together eight of those dang trochees in a row. No matter how you slice it, octameter is always kind of awkwardly long in English. I always try to read it as two separate, bite-size lines. But Poe doesn't let you do that by using a combination of alliteration, drawn-out thoughts, and off-center breaks. For example:
And the silken, sad, uncertain rustling of each purple curtainThe fourth trochee of the first line is "-certain." That should be the natural break. But we slip on the alliteration--"silken, sad, uncertain"--and slide right into the end of the thought. We dig in our heels after the fourth trochee, but the alliterative momentum and our own curiosity knocks us over into the fifth, sixth, seventh, and eighth trochees.
Thrilled me--filled me with fantastic terrors never felt before;
The second line has the off-center break I was talking about. Instead of giving us a nice comma after the fourth trochee ("-tastic"), Poe makes us take a breath after the first trochee: "Thrilled me." Even though the second line doesn't have the alliterative momentum, it has the thought momentum that pulls us forward into the second half of the line.
Finally, Poe uses an analog to the old idea of comic relief. After five lines of trochaic octameter, he gives us a bite-size trochaic tetrameter at the end of each stanza. For me, these serve as a sort of breather, but the bad kind, the kind of breather you take when you're swimming in from too far out in the water. You don't think you're moving, but you're slipping farther and farther out to sea. Only here, it's the hypnotic sea of The Raven.
Finally, the salt on the watermelon are the sprinkled in lines that are nearly comedic:
"Surely," said I, "surely that is something at my window lattice;That is, lattice, and thereat is. The man was a rhyming genius.
Let me see, then, what thereat is, and this mystery explore--
PS--I just learned the ravens can talk. This poem just went from fantastical to dadgum.