Iambic pentameter

Shakespearean Sonnet Basics: Iambic Pentameter and the English Sonnet Style

Shakespeare's sonnets are written predominantly in a meter called iambic pentameter, a rhyme scheme in which each sonnet line consists of ten syllables. The syllables are divided into five pairs called iambs or iambic feet. An iamb is a metrical unit made up of one unstressed syllable followed by one stressed syllable. An example of an iamb would be good BYE. A line of iambic pentameter flows like this: 

baBOOM / baBOOM / baBOOM / baBOOM / baBOOM. 

Here are some examples from the sonnets:

When I / do COUNT / the CLOCK / that TELLS / the TIME (Sonnet 12)

When IN / dis GRACE / with FOR / tune AND / men’s EYES
I ALL / a LONE / be WEEP / my OUT/ cast STATE (Sonnet 29)

Shall I / com PARE/ thee TO / a SUM / mer's DAY? 
Thou ART / more LOVE / ly AND / more TEM / per ATE (Sonnet 18)

Shakespeare's plays are also written primarily in iambic pentameter, but the lines are unrhymed and not grouped into stanzas. Unrhymed iambic pentameter is called blank verse. It should be noted that there are also many prose passages in Shakespeare’s plays and some lines of trochaic tetrameter, such as the Witches' speeches in Macbeth.