The classic sonnet--14 lines, ABABCDCDEFEFGG rhyming pattern, often in iambic pentameter--is defined as much by the nobility of its sentiment as by the lines of its structure. Some stirring examples:

"That time of year thou may'st in me behold..."
"Shall I compare thee to a summer's day?"
"When Rapparree pretends to know it all..."

Notice the trochees tripping lightly o'er the page...