Iambic tetrameter is a metrical line made up of four iambs, or four repeating pairs of an unstressed syllable followed by a stressed one. It often sounds natural and forward-moving, and poets use it in many short lyric forms, songs, and ballad-like stanzas.
A line in iambic tetrameter usually has eight syllables, though natural speech and poetic variation can make the rhythm less rigid than a simple count suggests.
Example
the MORning WIND aROSE aGAIN
and SHOOK the DEW from GRASS and TREE
Ap PAR..|..elled IN..|..cel EST..|..ial LIGHT,
The EARTH,..|..and EV..|..ry COM..|..mon SIGHT,