The first four lines of "The Solitary Reaper" announce the poem's broad themes and introduce the reader to its formal technique. The poem begins with apostrophe: the speaker addresses the reader directly, commanding them to "behold" and "stop here." The poem is thus an invitation—an invitation to contemplation. The speaker asks the reader to stand and watch as a Scottish woman—a "Highland Lass"—cuts a field of wheat with a sickle. The speaker uses the present tense throughout these lines. As a result, the reader may feel that they are standing next to the speaker, observing the scene together as it unfolds, listening to the reaper's song. Notably, however, each of the speaker's addresses to the reader are separated from the rest of the line by a caesura: even as the speaker invites the reader into the poem, he marks the reader's distance from the scene he describes.
In these lines, the speaker does not tell the reader much about the lass's song—yet. But the form of his poem may give the reader some hints about the song itself. The first four lines of the poem closely approximate a stanza of a ballad. At the time that Wordsworth wrote "The Solitary Reaper," the ballad was a folk form, in wide use across the British Isles for popular songs and lowbrow verse. It was not a highly literary form like the sonnet or heroic couplets. Instead, ballads often used everyday language to tell unpretentious stories of everyday life and love in the countryside and cities. Further, ballads were often collaboratively authored: one anonymous poet adding a stanza, another rearranging the order of stanzas, a third deleting stanzas or changing the theme, or writing new words to the same melody. Scottish poetry also makes prominent use of the ballad, in print and in popular song. Indeed, it seems likely that the reaper's song was a ballad or a piece of music emerging from the ballad tradition.
Ballads had a standard rhyme scheme and meter—though, as a popular form, these standards were rarely strictly upheld in practice. Traditionally, ballads rhyme in an ABCB pattern (the second and fourth lines rhyme, the first and third do not), with alternating lines of iambic tetrameter and iambic trimeter. The first four lines of "The Solitary Reaper" follow this pattern—almost. They do rhyme ABCB; but the first three lines of the poem are in iambic tetrameter followed by a single line of iambic trimeter. This means that the first four lines of the poem follow the pattern of a ballad, but with an extra foot in line 2—a relatively minor deviation from the standards of a genre whose standards are already loose. The speaker here seems to be imitating the formal dynamics of the reaper's song, in a sense recreating the reaper's song for the reader.
The first stanza of the poem is heavily end-stopped; it is enjambed only in lines 1 and 7. This creates a slow, contemplative reading experience: the reader is encouraged by the end-stops to ponder each line, to dwell on them meditatively. But the speaker also employs a subtle pattern of assonance, particularly on an /i/ sound, to bind together the stanza and keep the reader moving through it.