Meter

Iambic: an iamb is made up of two syllables where the stress (or accent) is placed on the second syllable. eg. "She CANnot FADE, though THOU hast NOT thy BLISS,

For EVer WILT thou LOVE, and SHE be FAIR!" (Keats, Ode on a Grecian Urn".

Counting the accented syllables, you come up with five beats, hence these lines are in iambic pentameter, a meter which always starts a line on a soft stress and ends on a hard. Iambic meter gives a kind of sing-song, often soothing rhythm which is why it's so often used for love poetry.

Trochaic: A trochee is essentially the opposite of an iamb -- two syllables, HARD soft. Trochees give a strong beat, often like an exclamation, and are commonly employed in nursery rhymes because they make quite an impression.

eg. "SANta CLAUS you FAT old GIT".

If you look at Shakespeare's sonnets, you'll find that the Bard often slipped a trochee into the first line to make an impact, which is just what it does.

Dactylic: Dactyls are three-syllable feet, HARD soft soft. DUM diddy... I think of it as a kind of blues beat.

eg. "VICtory LIVES in the HEART of the CELT,

GIFTed by BLOODstains that FLOW on through YEARS"

The dactylic line will often end on the strong stress, leaving a pause as you would find at the end of a song lyric.

Anapestic: An anapest is another three-syllable foot, soft soft HARD -- da da DUM. Anapests give a galloping feel to a line and are often used to describe action.

eg. "And the SHEEN of their SPEARS was like STARS on the SEA,

When the BLUE wave rolls NIGHTly on DEEP GaliLEE" (Byron, The Destruction of Sennacherib)

Meters can be mixed up and experimented with to strengthen a poem sonically. They needn't be employed only in rhyming poetry. Sound is important to consider in most poems -- they are, generally speaking, supposed to be read aloud. Ginsberg's "Skeletons" is a good example of contemporary poetry with a strong meter.