The first line, for example, appears to begin with two unstressed syllables followed by two stressed ones, while the second line unquestionably contains a trochee and an iamb and therefore forms a choriambic foot.
Although not one line of iambic hexameter appears, lines sometimes begin with a trochee or spondee or two, drift gently toward an iambic norm, and then depart from it.
A trochee is a metrical foot of two syllables, the first long and the second short.
We hear iambs, trochees , Virgil's hexameters, the Norse alliterative lines, each arranged in their various couplets, quatrains, choric stanzas, gnomic verses, and much more besides.
This is matched by the metre where, however, intricate use of trochees and dactyls gives a song-like quality to the verse.