What meter is used in Sonnet 18?
If you are referring to William Shakespeare's Sonnet 18, it is written in iambic pentameter. This means that there are five metrical feet per line (pentameter) and each foot contains an iamb which is identified by one unstressed syllable followed by one stressed syllable.
When marking meter on paper, unstressed syllables are usually marked with a backslash "/" and stressed syllables are usally marked with an "x."
Iambic pentameter was the most popular form of meter used during the Renaissance era and is also the most common form of meter used in sonnets.