How do those iambs really work? Can they go upside down? Backwards?

Answer 1

In poetry, an iamb (pronounced I-am, the "b" is silent) is a unit of meter or rhythm consisting of two syllables with the stress falling on the second syllable. For example, when Hamlet says "To be or not to be," that's three iambs in a row, since the line, when spoken aloud, sounds like this:

to BE or NOT to BE

A backwards iamb, a two-syllable unit of meter in which the stress falls on the first syllable, is called a trochee (pronounced TRO-key). The word "happy" is a trochee. Likewise the words "breakfast," "magnet," and "spider."

Most of Shakespeare's verse is written in iambs, but not all of it. One famous example of a speech written in trochees is Puck's speech at the end of "A Midsummer Night's Dream." The speech begins:

If we shadows have offended,
Think but this, and all is mended,

Say those lines aloud and you'll hear that the stress falls naturally on the first syllable in every pair:

IF we SHAD ows HAVE of FEND ed
THINK but THIS and ALL is MEND ed

Answer 2

No! Straight forward: da DA; two syllables, emphasis on the second.