We've said it before, and we'll say it again: "Metrical Feet" sounds just like one of those mnemonics you learn in school, such as "Thirty Days have September, April, June, and November" or "i before e except after c." To be fair, "Metrical Feet" isn't as easy to memorize as those, and it's about a slightly more complicated topic, but the principles are the same.
"Metrical Feet," like other such mnemonics, uses rhymes, repetition, and unique imagery in order to facilitate learning. The sound of the poem is totally serving its sense; every sound helps us understand and remember what we're learning as we read.
Take lines 9-10 as an example:
First and last being long, middle short, Amphimacer
Strikes his thundering hoofs like a proud high-bred Racer.
Can't you imagine a ten-year old reciting this? Or can you see yourself reciting this the next time you're called upon to explain what an amphimacer is? Just think of a "thundering…racer"!
The same goes for the lines about the spondee. The letter "s" is used in six straight words there: "solemn sort / Slow spondee stalks, strong foot." The alliteration makes these lines super easy to remember, doesn't it?
So take a moment and read the poem aloud to yourself. See if you can spot alliteration, assonance, and rhymes that help you remember just what an amphibrach or a trochee is. Do the sounds of the poem help you? They certainly helped Shmoop.