How Does the Poet Turn the Words into Poetry?

       No matter how different the form and objective, all poetry contains three elements: rhythm, sound effects, and metaphor.  We might say about a prose work, "This writer's style is very poetic," i.e. it makes good use of subtleties of rhythm, or it relies on extensive use of metaphor for effect.  Let's talk about rhythm first, using as an example the Robert Frost poem that was reproduced in the post "What IS This Thing Called Poetry?"  I'll reprint it here (I've also marked the rhyme scheme; we'll get back to that later).
 

Whose woods these are I think I know, [a]

His house is in the village, though; [a]
He will not see me stopping here [b]
To watch his woods fill up with snow. [a]

 My little horse must think it queer [b]

To stop without a farmhouse near [b]
Between the woods and frozen lake [c]
The darkest evening of the year. [b]

He gives his harness bells a shake [c]

To ask if there is some mistake. [c]
The only other sound's the sweep [d]
Of easy wind and downy flake. [c]

The woods are lovely, dark, and deep, [d]
But I have promises to keep, [d]
And miles to go before I sleep, [d]
And miles to go before I sleep. [d]

       Poetic rhythm (meter) is quantified according to certain conventions.  It's usually measured in "feet," i.e. syllabic units with a particular stress pattern.  The Frost poem is classic iambic tetrameter, i.e. four feet to the line, with each foot containing two syllables, stressed "ta-DAH." Thus the first and last lines are quite regular and exemplify this scheme well:
whose WOODS | these ARE | i THINK | i KNOW. 
to WATCH | his WOODS | fill UP | with SNOW|. 

       A skilled poet will vary the feet within the selected framework in order to avoid monotony.  Thus, the second line  would never be read like this in normal speech:  
his HOUSE | is IN | the VILL | age THOUGH. 
It reads in a natural voice:
his HOUSE | is in | the VILLage | THOUGH. 
(If you interested in technical terms, "is in" is a Pyrrhic foot -- two unstressed syllables; "the VILLage" is an amphibrach (unstressed-stressed-unstressed); and "THOUGH" is a half of a spondee (stressed-stressed).  [I think a foot with a single stressed syllable has some other name, but I can't recall it or find it at the moment.]
       The third line reads (at least in my ear; this is not a cut-and-dried process) as:
he WILL not | SEE me | STOPping| HERE. You get an amphibrach, a trochee, another trochee, and half a spondee, all within the framework of tetrameter (four feet to the line).

       You might say (and I'm sure many students say it every day), why bother with this kind of boring analysis? My answer is that it can provide an awareness of how a poet achieves natural, conversational rhythms without losing the basic metrical pattern that he selected.

       You'll notice Frost uses a number of two-syllable words in the lines (village, stopping, farmhouse, evening, harness).  They tend to tie the lines together and ease up the "thum-PAH" of the designated meter.
       But then you get these two lines:
The only other sound's the sweep
Of easy wind and downy flake.
       The regularity of the rhythm here reinforces the sense of lulling quiet and smoothness of the process of wind and snow.  What if he had written the following (removing the contraction from "sound's")?
The only other sound is the sweep
of easy wind and downy flake.
       The first line there limps horribly; it almost hippity-hops, because you have to speed up to say "sound is the" in order to insert the extra syllable.  You've lost your handle on the meter and converted it into prose. This is where a lot of beginning poets falter; they have a tin ear for the rhythm. 
       Furthermore these two lines are run-on grammatically; all the other lines have a natural break at the end.  This also adds to the sense of hypnoptic smoothness.

       And then the final stanza: 
The WOODS | are LOVEly, || DARK and | DEEP. 
       You get iamb, amphibrach, trochee, spondee.  This line contains a cesura -- a slight pause after "lovely."  The isolation of the two heavy syllables near the end of the line reinforces the significance of the words.
But I | have PROMises | to KEEP. 
       "Promises" is the only three-syllable word contained in the poem and it's located centrally in the line, which is pretty much reduced to three feet.  This puts the emphasis on the word "promises."
       And then the final pair of lines, where the rhythm returns to very regular iambic tetrameter:
And miles to go before I sleep,
And miles to go before I sleep.
       That repetition is one of the most important elements of the poem.  The regularity of the meter combine with the repetition to increase the sense of that hypnotic weariness, that sameness -- putting one foot in front of the other in what seems an endless forward trudge.

       Now of course the effect of a poem is not achieved entirely by meter.  Let's consider the elements of sound -- rhyme, assonance (repetition of vowel sounds), consonance (repetition of consonant sounds), and alliteration (repetition of initial consonant sounds).
       Rhyme patterns are usually described in terms of alphabetic letters.  Thus a basic four-line ballad stanza rhymes a-b-c-b, as in a stanza of a poem ("The Dowie Houms o' Yarrow"), which I used as an epigraph in "The Termite Queen," v.2:
Four he hurt, an’ five he slew, [a]
On the dowie houms o’ Yarrow, [b]
Till that stubborn knight came him behind, [c]
An’ ran his body thorrow. [b]
       In the Frost poem the rhyme scheme is more subtle; the rhyming words are very simple, but they are used in an interwoven pattern.  I marked the scheme in the poem printed above.  The end word of the third line of each stanza forms the basic rhyme of the next stanza, until one gets to the final quatrain, where all four lines pick up the third line from the third stanza.  This additional repetition acts as yet another reinforcement of the poet's weariness with the inescapable forward progression of life.
       Actually, assonance, consonance, and alliteration don't play that large a role here.  The phrase "watch the woods" is alliterative, but otherwise the only noticeable use of consonance is again in the lines:
The only other sound's the sweep
Of easy wind and downy flake.
       Also noticeable here is the assonance of sweep and easy, and sound and downy, again suggesting the smoothness and silence of the wind and snow.

       Finally we need to talk about the most important element of all: metaphor.  What is metaphor?  Technically, it's a figure of speech in which one item is totally identified with another, and it's usually contrasted with simile, which is mere comparison.  An example of a metaphor is Keats' wonderful line in "Ode on Melancholy," where a person is spoken of as one who "can burst joy's grape against his palate fine."  Joy IS a grape; if he had written, "Joy is like a grape that one can burst against his palate," that would have been a simile.  If something actually partakes of the identity of something else, that constitutes a much stronger statement.
       However, the term "metaphor" can also be applied more broadly, as any substitution of one thing for another, any symbolic representation.  I plan to use it that way in my discussions of poetry. 
       All poetry deals in metaphor in this broad definition.  If it doesn't, it can't be called true poetry.  Between the prosaic words of the metaphor and the reader's perception of the metaphor is the gap where the poetry lies.

       In the Frost poem, I have wondered at times about the initial remark concerning the owner of the woods.  Is this simply a nod to reality?  I've decided that the implication (metaphorical) is that, as part of the natural world, the woods belong to God, whose house in "in the village," i.e. the village church.  Maybe this is a standard interpretation; I haven't read any criticism of the poem, but however that is, I personally just thought of it.     
       I believe the "little horse" IS a way to connect the scene to reality, although "the darkest evening of the year" could imply that the poet is at the winter solstice of his life, in a dark and depressed state.
      Actually the entire poem is a metaphor, symbolizing the longing for death to take us beyond the distresses of daily life.  The poet never says, "Death is like a dark wood that makes us want to enter it, experience and yield to its darkness, and escape our responsibilities."  Obviously, that would be much weaker, more sententious, and even cliched.  Death is also seen as sleep -- nothing new there, but we have the implication of death from the cold; you lie down in the snow and you go to sleep peacefully and never wake up.  Death becomes a painless process of escape.  By couching that concept totally in a deceptively simple, narratively structured metaphor, Frost has written a strong and moving poem that becomes unforgettable.

       If anyone would like to add anything to my interpretation, I'd love to entertain remarks.