Dickinson frequently used a metrical form called common meter. Common meter features alternating lines of eight and six syllables. When analyzed using conventional methods of scansion, this structure is often equivalent to alternating lines of iambic tetrameter and iambic trimeter. (Recall that an iamb is a metrical foot with one unstressed syllable followed by a stressed syllable, as in the word “to-day.”) The alternation between four-foot and three-foot lines creates an overall rhythm that has a strong sing-song quality. And indeed, common meter frequently appears in ballads, songs, and popular hymns. For a typical example of common meter, consider the poem’s second quatrain (lines 5–8):

And sweet- / est  in / the gale  / is heard;
And sore / must be / the storm
That could / a-bash / the litt- / le bird
That kept / so man- / y warm.

As the breakdown above shows, this stanza presents a perfectly regular example of common meter: the rhythm is strictly iambic throughout, and the lines alternate between tetrameter and trimeter. The result is a cheerful-sounding meter that echoes the “sweetness” of the hope-bird’s song.

Though Dickinson generally deploys common meter with perfect regularity, it’s notable that the poem’s opening line is irregular:

Hope” is the / thing with / feath-ers

Start by noting that this line only has three feet even though, according to the usual pattern of common meter, it should have four. Also consider that, in contrast to the iambic rhythm that predominates in the rest of the poem, the opening line consists of a combination of one dactyl (stressed–unstressed–unstressed) and two trochees (stressed–unstressed). The use of a three-syllable foot as the poem’s opening is surprising. But perhaps even more significant is the fact that the meter of the entire line uses what’s known as falling rhythm. Falling rhythm is the term for any rhythmic pattern that starts with a stressed syllable and moves to unstressed syllables. This movement from stressed to unstressed creates a stumbling rhythm that suggests a downward trajectory. Taken together with the fact that the line falls short of its expected length, the use of falling rhythm exists in tension with the bird-like image of hope presented in this line. However, immediately after defining hope in this way, the speaker shifts to the rising rhythm associated with iambic meter (lines 2–4):

That per- / ches in / the soul,
And sings / the tune / with-out / the words,
And nev- / er stops – / at all,

This shift from falling to rising meter mimics the hopeful image of a bird taking flight.