Nonetheless, I resisted the strong temptation to save them
In these lines the speaker tells us that it was difficult to put on the socks, that he would have rather kept them nice and new, like a comic-book collector who leaves the first issue of Superman in its sleeve.
But here, instead of resisting the temptation to open and read the comic, the speaker has to resist "the strong temptation" to not use the socks. Pull 'em on, man!
the way schoolboys bottle fireflies,
These lines are a metaphor for the speaker's impulse to save the socks. This temptation is compared to the way that kids keep fireflies in a jar.
The metaphor compares this desire to an innocent, but at the same time, kind of cruel practice. Catching fireflies is a quick way to bring the reader back to childhood, summertime, and carefree days. But keeping the poor fireflies in a bottle, in retrospect, is a kind of a mean thing to do.
Another metaphor here compares the desire to keep the socks new to a scholar who keeps "sacred documents" safe in an archive. Think of the Declaration of Independence in the special case that protects it from light and air in the Smithsonian. The socks aren't supposed to be kept away from the world. They're supposed to be used!
I resisted the wild impulse to place them in a cage of gold and daily feed them birdseed and rosy melon flesh.
In another metaphor, now the socks are compared to pet birds. The speaker would like to cage them, and feed them. But even though the cage would be a golden one, and the food would be delicious (rosy melon flesh, anyone?), the socks are not meant to be trapped and kept on display like pets.
This metaphor, along with the two that precede it comparing the socks to sacred documents or fireflies, might be a stand-in not only for the socks, but for poetry itself. The idea of this beautiful cage that turns the birds into mere decorations is kind of like what a poem can do to its subject.
Think about it: if making up beautiful metaphors about objects is what poetry usually does, then what happens in this poem? The effect of reminding us constantly about just how ordinary, but at the same time, beautiful, these socks are, is the opposite of what an ode traditionally does. Whereas an ode might usually elevate something (think of that Grecian urn), this poem does praise the socks, but also doesn't go too far and remove them from reality.
This is part of the poem's overall effect, which is to praise an ordinary object, but also not to remove it from reality. There's a back-and-forth between figurative language and the reminder that this is an ordinary, everyday object. It's a nudge to find the poetry in everything, and not see poetry as an elite practice, removed from the day-to-day.
Like explorers who in the forest surrender a rare and tender deer to the spit and eat it with remorse,
These lines are about necessity and beauty. The speaker is compared to explorers who kill and eat a "rare / and tender deer." The socks are compared to the deer in this simile.
The idea is that wearing the socks, rather than just admiring them, is kind of like being hungry in the forest. To survive, you're going to have to eat something, probably something you killed. But what if the prey is a beautiful, young animal? You're going to have to swallow your poetic appreciation and just pull the trigger, or let the arrow fly, and eat the poor, pretty animal.
These lines contribute to the overall theme, which is about finding beauty in the everyday without having to remove the ordinariness from the beautiful object.
However, the speaker does feel some remorse about having to do this. Yet, it's about survival. There's not much you can do if you want to stay on the island.
I stuck out my feet and pulled on the handsome socks, and then my shoes.
After all the figurative language of the previous lines, these ones are really matter-of-fact. The speaker puts on the socks, then some shoes.
This is kind of like landing after skydiving. There's a lot of beauty, wonder, and awe, and then suddenly: the ground. The speaker has had us comparing the socks to all sorts of magical, beautiful things, and now suddenly, once they're on the feet, we're back in the realm of reality. But have the socks lost their magic? Let's read on…