Identify the simile and metaphor in the 3rd stanza and discuss their effectiveness in creating the poet's meaning
Okay, well, if we need to find the simile and metaphor, then we should define the two terms and then explore that pesky third stanza. A simile is a comparison that uses the words "like" or "as," while a metaphor is a comparison that doesn't use those words. Now let's look at the entire third stanza of "Dover Beach":
The Sea of FaithWas once, too, at the full, and round earth’s shoreLay like the folds of a bright girdle furled.But now I only hearIts melancholy, long, withdrawing roar,Retreating, to the breathOf the night-wind, down the vast edges drearAnd naked shingles of the world.