"The Express" by Stephen Spender is a semi-meter free verse poem of 27 lines with a presence of iambs in lines that can be scanned according to pentameter. Examples of places where the traces of iambic pentameter appears are:
She pass' -es the hous' -es which humb' -ly crowd outside', 5
Where speed' throws up' strange shapes' , broad curves' 9
Free verse is written according to the theory that metrical considerations of rhythm and patterns of repetition (feet) hinder expressions of thought more often than they enhance such expression. Poets writing free verse consider metrical elements to be another poetic devise available for use to meet desired ends. Spender uses shades of meter to draw attention sections of his poem, for instance after "she" bolws "her whistle screaming at the curves" and continues to gain momentum and speed.
Similarly, there is no rhyme scheme, yet Spender does include two instances of rhyme. The first is in lines 7-9:
Of death, printed by gravestones in the cemetery.
Beyond the town, there lies the open country
Where, gathering speed, she acquires mystery,
End rhymes join the lines with "cemetery," "country," and "mystery." Bear in mind "cemetery" carries a British pronunciation rhyming it with "country" and "mystery." The second is,
Beyond the crest of the world, she reaches night
Where only a low streamline brightness
Of phosphorus on the tossing hills is light.
where "night" and "light" alternate with "brightness." Spender points to the vitality of the express locomotive by juxtaposing the "mystery" of its "gathering speed" in the "open country" with the still death of the "cemetery." Then he dramatizes the distance the express travels by defining the brightness of the light at the far reaches of the world by the word "night": brightness so far removed that it's part of night.
The underlying metaphor personifies the express locomotive and compares "her" to a queen: "But gliding like a queen', she leaves the station." The theme is the might and prowess of the locomotive express train ("The black statement of pistons"). The theme is illustrated in the closing lines, 25, 26 and 27:
Ah, like a comet through flame, she moves entranced,
Wrapt in her music no bird song, no, nor bough
Breaking with honey buds, shall ever equal.
Some poetic devices Spender uses are personification, as stated, which is carried throughout the poem through the repetition of "she" and "her." Spender employs metaphor, for example, the comparison of the "landscape" to the railway tracks, or lines: "Streaming through metal landscapes on her lines, ...." Spender also uses a metaphor to compare the express's whistle to a song "she begins to sing":
It is now she begins to sing --- at first quite low
Then loud, and at last with a jazzy madness ---
The song of her whistle screaming at curves
Spender employs two similes. The first compares the parallel train ties to bullet trajectories: "And parallels clean like trajectories from guns." The second compares the express to a comet: "Ah, like a comet through flame, she moves entranced, ...."