Let's tackle the rhyme first, since that's pretty straightforward. See how the poem is divided up into little four-line chunks (stanzas)? Basically, the second and fourth lines in each one of those stanzas rhyme with each other. We'll show you how that works in the first stanza by putting the rhyming words in bold
The day is done, and the darkness (A)
Falls from the wings of Night, (B)
As a feather is wafted downward (C)
From an eagle in his flight. (B)
Easy, huh? And it repeats over and over: Night/flight, mist/ resist, pain/rain, and so on. See those letters we put up there too? They give us another way of marking out what's called the rhyme scheme. So the rhyme scheme for this poem, using the letters from up above, goes ABCB, over and over again.
Now for the meter. We think Longfellow is trying to be a little bit sneaky (or maybe just playful) with the meter here, because it isn't super-regular like the rhymes. You could probably spend a lot of time working out all the quirks, but let's check out the basics. Each line has three stresses, or beats. We'll show you that by putting them in bold:
The day | is done, | and the dark|ness (8 syllables)
Falls from | the wings | of Night, (6 syllables)
As a fea|ther is waft|ed down|ward (9 syllables)
From an ea|gle in | his flight. (7 syllables)
You can hear this by sounding it out, too. The stresses fall at different places in the line, but there are always three of them. We call this kind of three-beat line trimeter.
Also notice how, in the stanza above, the first and third lines have more syllables than the second and the fourth lines. For the most part, the stanzas in this poem alternate long and short lines, just like that. Not always, though. In some cases the first and second or the third and fourth lines will be the same length (check out the last two lines in the poem for example).
We won't take you any farther down the rabbit hole on this one, but we think there might be a reason for this weirdness. Remember how Longfellow talks about the "restless pulse of care" (line 34). This poem is all about being stressed and tired and out of whack. In a way, the meter of this poem recreates that feeling by being a little stressed and confused and restless itself.