Wordsworth's “Lines Written in Early Spring” follows a fairly conventional pattern of rhyme and meter. In terms of the former, the rhyme scheme is abab right throughout the poem, as we can observe in the second stanza:

To her fair works did Nature link (a)
The human soul that through me ran (b)
And much it grieved my heart to think (a)
What man has made of man. (b)

Wordsworth isn't trying to be experimental here. And so he uses a regular rhyme scheme, perhaps the most regular rhyme scheme in English language poetry, to put into words his innermost thoughts.

In the poem, Wordsworth wants to say something very important indeed. He is lamenting how man has departed from nature in making a complete mess of the world.

If man had followed nature in the Romantic fashion, then all would've been well. But he hasn't, and because of this, the human world, with all its greed, violence, war, and bloodshed, has become a very grim place indeed.

The seriousness of Wordsworth's message is reinforced by the abab rhyme scheme, whose repetition drills into the reader's mind the due solemnity of what the speaker has to say.

It is also reinforced by the use of iambic tetrameter, one of the most common poetic meters in English language verse. Iambic tetrameter consists of four iambs in a line of verse. An iamb is a metrical foot in which an unstressed syllable is followed by a stressed syllable, giving us a kind of da-DUM rhythm, as in the word “desTROY,” for example.

Iambic tetrameter is often used in traditional ballads. And although “Lines Written in Early Spring” is not a ballad, it harks back, in true balladic fashion, to some idealized world. In the case of Wordsworth's poem, that means the world of nature, in whose beauty and tranquility can be seen a stark contrast to the human world with all its turmoil.

Wordsworth uses a combination of iambic tetrameter and the more compact and economical iambic trimeter—three iambic feet to the line—in each stanza:

The birds around me hopped and played,
Their thoughts I cannot measure:—
But the least motion which they made
It seemed a thrill of pleasure.