"Ozymandias" by Percy Bysshe Shelley is a poem that utilizes a slightly irregular version of the sonnet form.

The rhythmical pattern of the lines is iambic pentameter. To unpack this, we describe poetic lines in terms of two things, the smallest repeated rhythmical unit of the line (called a "foot") and the number of times the foot is repeated in the line. Shelley's poem uses an iambic foot, meaning that its basic pattern is that of an unstressed followed by a stressed syllable. This pattern is repeated five times in each line, and therefore we refer to the meter as pentameter, a word meaning five (penta-) measures (meter). 

As the poem is comprised of fourteen lines in a somewhat regular rhyme pattern, it is a sonnet. However, the rhyme pattern is not completely regular. The first two stanzas are irregular open quatrains (abab acdc), appearing to follow the pattern of an English sonnet, but the final six lines appear a variant on the sestet of an Italian sonnet (ece fef). 

Thus perhaps the best description is that this is an iambic pentameter sonnet with a slightly irregular or hybrid rhyme scheme. 

"Ozymandius" is written in iambic pentameter, which means that there are ten syllables in each line of the poem in five pairs of two, with the first syllable in each pair unstressed and the second syllable stressed.

I met/ a trav/-eller from/ a dis/-tant land/

The first eight lines are the traveller's description of what was seen in the desert, recognizing the artistic skill that had sculpted the "frown and wrinkled lip and sneer of cold command" with great skill. The final six lines point out the irony of the great power and majesty claimed by the figure that had been portrayed, now a "colossal wreck, boundless and bare."

The rhyme scheme is the trickier element in the analysis of the poem's structure. Shelley uses a very complicated interconnection of the rhyming words at the end of the lines to emphasize the discontinuity and irony contained within the poem's story. The rhyme pattern can be described as being "abab acdc ece fef".

What are the rhyme scheme and meter of the poem "Ozymandias"?

"Ozymandias" is written in iambic pentameter. This is a meter in which a line has five pairs of two syllables, for a total of ten syllables. In an iambic meter, the stress falls on the second syllable in the pair. For example, the opening line reads as follows:

I met a traveller from an antique land

The bolded words indicate where the stresses fall. Critics have noted that some of the lines in the sonnet don't appear to follow iambic pentameter precisely (unless you read them in an unnatural way), but in general, the poem has the "da-DUM da-DUM" meter of iambic pentameter—and we can only quibble as to where the stresses fall because we don't know how Shelley would have read the poem.

As for rhyme scheme, the first four lines follow the pattern of the Shakespearean sonnet: A-B-A-B, with "land" and "sand" and "stone" and "frown" rhyming: however, stone and frown don't exactly rhyme. This is called a slant rhyme. Some scholars argue that "stone" and "frown" rhymed more closely in Shelly's day, but again, we don't know, as there's no way to know how Shelley would have read it.

After this, the next quatrain or four line group rhymes A-C-D-C: "command" rhymes with "land" and "sand", and then "read" and "fed" rhyme. In the next quatrain, lines 9–12, the rhyme is E-D-E-F. Usually a sonnet ends on rhyming couplet, meaning the last two words rhyme with each other, but in this case, the rhyme is E-F: "bare" rhymes with "despair" and "away" with "decay." To me, this is very effective, because it slows down the end of the poem and gives it a hollow, desolate sound.

Despite some possible variants, this sonnet is written in a traditional iambic pentameter meter and with end rhymes that vary a bit from traditional sonnet patterns but still work effectively.