Blake's Songs of Innocence and Experience aren't called "songs" for nothing. In both form and rhythm, "The Lamb" bears similarities with Charles Wesley's hymn beginning "Gentle Jesus, meek and mild," from Hymns for Children, published in 1763, several decades before the Songs of Innocence:
Gentle Jesus, meek and mild, Look upon a little child; Pity my simplicity, Suffer me to come to Thee.
Not only does Blake borrow the "meek and mild" line and the stuff about lambs, but he mimics this hymn's simple AABB rhyme scheme and trochaic rhythm. These two stylistic points are common to many hymns, perhaps because they make the songs easier to memorize and identify for your average person at the local church. They have the air of nursery rhymes.
A trochee is a kind of rhythm that repeats the pattern of an stressed beat followed by an unstressed one: "Gave thee life & bid thee feed. / By the stream & o'er the mead". In English poetry as a whole, it's more common for the unstressed beat to come first, but in hymns, trochaic meter is just as standard.
The rhymes in "The Lamb" are outrageously simple. Blake rhymes "thee" with itself four times and mostly sticks to single syllables, like "feed" and "mead," "mild" and "child." Blake throws us only the slightest of curveballs with the slant rhyme between "name" and "Lamb."
The poem has two stanzas with ten lines each. The first two and last two lines of each stanza are repeated like the chorus or refrain of the song. These lines have six beats, and they serve as bookends to the middle six lines, most of which have seven beats.