Rhythm in Poetry - Deviation

So as soon as we know all about rhythm in poetry, we deviate. Of course we do. Not just through sheer bloody mindedness, but to use the effects on the reader.

Pauses

Poems are presented as lines on a page. (We're talking about reading here, not performing. That for another day.) And the very fact that there are lines with and ending, lead the reader towards wanting to pause at the end of each line. Maybe for a breath, maybe just because the phrase naturally ends at the end of the line.

As I was going to St Ives

These are called end-stopped lines, as apposed to

As I was wandering along the road towards

with the second  line, you keep on reading to the next line. (Where is the poet going?)

End-stopped lines encourage the reader to pause and consider the words or feelings or images just raised.

Shall I compare thee to a summer's day?
Thou art more lovely and more temperate.

So what about the second version? Lines which are not naturally end-stopped are called run on lines or enjambment. Why would a poet use this technique? To speed up a reader, to generate a sense of hurry.
"Enjambment" comes from a French word meaning to put one's leg across, or to step over, so think of it as getting your leg over.

Wikipedia gives the example of one of my favourite poets for uses of enjambment, e e cummings.

i carry your heart with me(i carry it in
my heart)i am never without it(anywhere
i go you go,my dear;and whatever is done
by only me is your doing,my darling)

There's all sorts of double meanings and a sense of ugency to read on. Beautiful.
Lastly for now, caesura. Cool name. All it means is a pause within a line, a hiccup if you will. It can be used to break the monotomy of a metre or perhaps to emphasize a word or a phrase.

How do I love thee? Let me count the ways.

 Or another of my favourite poems. Those Winter Sundays by Robert Hayden.

Sundays too my father got up early
And put his clothes on in the blueback cold,
then with cracked hands that ached
from labor in the weekday weather made
banked fires blaze. No one ever thanked him

 The caesura in the last line of the stanza. Gets you right in the gut.