Throughout the first chapter of this novel, Ray Bradbury employs some sort of imagery on nearly every page. However, most of this imagery is aimed at proving a contrast between Montag's world—the world of the firemen—and Clarisse's world. Bradbury employs his imagery by using a series of metaphors and extended metaphors. 

One of the most obvious ways Bradbury employs imagery in this chapter is by the constant comparison of those in the firemen's world to insects or serpents. The novel begins with a very vivid description of the firemen burning down a house with "the great python spitting its venomous kerosene upon the world." Then, as Montag watches the house that was full of books burn, he "strode in a swarm of fireflies." The metaphors continue as Montag compares the mechanical hound that is a stand-in for the traditional firehouse's dalmatian to "a great bee come home from some field where the honey is full of poison wildness, of insanity and nightmare..." and later to "a moth in the raw light, finding, holding its victim, inserting the needle..." Even in it's actual description the hound sounds like a giant spider: "[T]he Hound had sunk back down upon its eight incredible insect legs."

Montag's world extends beyond the dangerous, insect-ridden firehouse to a cold and dark home life. When Montag comes home after his first interaction with Clarisse, he walks into his home and compares it immediately to a "mausoleum after the moon had set." He goes on with a vivid description of his home:

"Complete darkness, not a hint of the silver world outside, the windows tightly shut, the chamber a tomb-world where no sound from the great city could penetrate."

Bradbury then continues with the insect imagery by comparing the music coming from his wife's Seashells (what we would call earbuds) being called "mosquito-delicate" with an "electrical murmur of a hidden wasp snug in its special pink warm nest."

Meanwhile, the world Clarisse shows Montag is beautiful and slow. Twice in the chapter, Montag compares his wife to a praying mantis, but in this chapter, he says Clarisse's face is like that of a clock in the middle of the night:

"[Y]ou waken to see the time and see the clock telling you the hour and the minute and the second, with a white silence and a glowing, all certainty and knowing what it has to tell of the night wiftly on toward further darknesses but moving also toward a new sun."

In addition, Clarisse provides several strong images to Montag at the beginning of the book that contrasts the insect-filled, fast world. She tells him that "there's dew on the grass in the morning" and "...if you look ... there's a man in the moon."

Bradbury provides all of these images as a way to provide contrasts between the two worlds and to indicate that the world run by the firemen is a cold, fast, insect- and serpent-filled one, while the world of books is slow and timeless.

Some more striking imagery is illustrated in descriptions of Clarisse. She is the first person to provoke new thoughts in Montag. This enables him to question why and how she thinks differently but more significantly, she gets him to question himself. As such, he literally and figuratively (hence the following imagery) begins to see himself differently in her eyes: 

He saw himself in her eyes, suspended in two shining drops of bright water, himself dark and tiny, in fine detail, the lines about his mouth, everything there, as if her eyes were two miraculous bits of violet amber that might capture and hold him intact. 

How like a mirror, too, her face. Impossible; for how many people did you know that refracted your own light to you? 

Given these images and those that follow (of Montag's home), note the sharp contrast between Montag's vivid descriptions of Clarisse and the dark, sterile descriptions of his home with Mildred. After his conversation with Clarisse, Montag is ruminating on the question of whether or not he is happy. Montag, still with the question in mind, must be aware of this transition from his thought-provoking discussion with Clarisse to his entrance into his boring routine of life. Entering his house, he describes his home like a tomb: 

It was like coming into the cold marbled room of a mausoleum after the moon had set. Complete darkness, not a hint of the silver world outside, the windows tightly shut, the chamber a tomb world where no sound from the great city should penetrate. 

An excellent example of imagery comes right at the start of the novel, which shows how content and proud Montag is of his job burning books. His love of burning, which has been instilled by years of indoctrination, appears in the connections his mind makes:

With the brass nozzle in his fists, with this great python spitting its venomous kerosene upon the world, the blood pounded in his head, and his hands were the hands of some amazing conductor playing all the symphonies of blazing and burning to bring down the tatters and charcoal ruins of history.
(Bradbury, Fahrenheit 451, Google Books)

The imagery in that sentence includes the "great python" of the kerosene hose, which feels alive because of the pressure inside and "spits venom" into the house; venom is harmful, and so is kerosene. Montag's hands, which recur throughout the novel as almost a separate character, are shown as "the hands of some amazing conductor," playing music of destruction instead of creativity. These images show the power of Montag's job, the animal connotations which also recur throughout, and the way destruction is glorified in this future society.