In addition to the answer by akannan, which is an excellent answer, you may find that your teacher is interested in your knowing about different types of poetic devices.
Longfellow is using a type of rhythm in the poem that reminds you of the galloping beat of the horses hooves. 9 syllables per line is almost iambic pentameter which should contain 10 syllables per line with a stressed and unstressed syllable per "meter foot".
Longfellow uses his stanzas to group different phases of Paul Revere's ride together. His stanzas are not of consistent length, but the length of each stanza either moves the reader along or slows the reader down to emphasize the passage of time.
He also used a variety of poetic devices to convey urgency and fear to the reader regarding the epic ride of Paul Revere.
The watchful night-wind, as it went
Creeping along from tent to tent,
And seeming to whisper, "All is well!"
A line of black, that bends and floats
On the rising tide, like a bridge of boats.
As it rose above the graves on the hill,
Lonely and spectral and somber and still.
Longfellow uses extended simile and metaphors to make comparisons that stick in your mind. There is a thrill of doing this rushed thing by moonlight only. The comparisons are easily remembered and quoted to this day.
Longfellow ends his poem with an open rather than a closed syllable allowing you to have your mouth open at the end of the poem. This gives the reader a feeling of exhaustion and even allows a sigh. It is as though the reader has been on the ride with Paul Revere.
There are several elements that enhance the meaning of the Longfellow's poem. The first would be present in the opening lines, whose tone is one of calling out to others in telling a story, regaling in a glory laden event in history. Such a tone establishes the feeling that what is to be experienced is to be of mythic proportions. The imagery of Revere rowing in the dead of night, waiting and examining the canvass for the impending British is enhanced with such pictures as Revere rowing the waters with "muffled oar," enhancing the danger present and stealth needed in Revere's successful execution of his mission. In addition to this, Longfellow's description of the British Somerset is filled with ominous and foreboding, almost to enhance the palpable sensation of fear present. The tone of intrigue and silence, a calm before the storm, is also employed throughout the rising conflict phases of the poem. This mood is replaced with intensity and Longfellow describes the feverished speed of Revere's mare flying through Lexington and Concord warning of the British's impending presence. Another use of poetic element would be the use of rhyme/ meter throughout the poem, but specifically in the line "One if by land, and two if by sea." The crisp rhythm of these lines have made them an almost indispensable component of American History and this poem.
There are plenty of elements to consider in Longfellow’s poem. The first you should notice upon reading in the beginning stanza is the use of rhyming couplets, ‘’listen my children and you shall hear of the midnight ride of Paul Revere. ‘’ In total there are ten stanzas with the initial one having five lines and the rhyme scheme of aabba. The rhyme scheme for the next stanza following that one is ababccddd. Each stanza has its own rhyme scheme you see. The third stanza, like the first, also uses rhyming couplets. Rhyme and meter are used throughout this poem and sounds of words are repeated, therefore employing repetition. The meters mostly used are iambic and anapest, and give off a rhythm like that of a horse’s gait. A figure of speech, simile, is used in Longfellow’s words ‘’as the moon rose over the bay,’’ used to describe the passing of time. Also, alliteration and consonance is indicated in the line ‘’ and the spark struck out by the steed, in his flight.’’ Another example of alliteration is ‘’lonely and spectral and sombre still.