Iambic Verse
We can tell just by looking at "The Altar" that its meter is irregular (i.e., it doesn't follow a set pattern). Some lines are shorter than others. They have to be, otherwise Mr. George Herbert would not have been able to arrange them in the shape of a little altar like he's done. Now we say irregular, but there is actually some predictability here. Every line is comprised of iambs. So what's an iamb? We're glad you asked, Shmoopers. An iamb is the most common type of beat in English poetry, and it consists of an unstressed syllable followed by a stressed syllable.
The first two lines of the poem, then, are in iambic pentameter, the most common meter in English poetry:
A broken ALTAR, Lord, thy servant rears. (1)
You should hear five iambs in a row there: daDUM daDUM daDUM daDUM daDUM. Lines 3-4, meanwhile, are iambic tetrameter, which means they contain four iambs, whereas lines 5-12 are iambic dimeter, which means that they only have two iambs:
Meets in this frame
To praise thy name. (11-12)
We should also mention that the poem is kind of like a nice little sandwich when it comes to meter: two lines of pentameter, two lines of tetrameter, eight lines of dimeter in the middle, then two lines of tetrameter, and finally two lines of pentameter again to wrap things up—yummy.
In addition, "The Altar" also has a nice little rhyme scheme to go along with its pretty little shape. It is composed of seven couplets, which are just successive lines that rhyme with each other (the rhyme scheme is AABBCCDDEEBBGGHH, in which each letter represents an end rhyme sound). If you look closely, you'll notice that the "B" rhyme occurs four times, partly because the speaker uses the word "frame" twice (hmm, must be an important idea).
So, putting this all together, we could say that we have a poem that is both regular and irregular. All the lines contain iambs, but there are at least three types of meter (iambic pentameter, tetrameter, and dimeter) going on. The poem contains seven different rhyming sounds (remember, the "B" rhyme repeats itself). So… what do we make of this? Well, the speaker is a little unsure of himself. He knows he is imperfect (hence the irregularity), and he knows that someday he might die or stop preaching (that's what he means by holding his "peace").
The altar the speaker describes is both a sturdy, stone structure and also one that is broken. The poem itself is the same way: regular and irregular, neatly organized and yet a little ragged. In other words, the poem's shape resembles an altar but so do its other formal elements (rhyme and meter). Pretty neat, eh?