The poem is written in iambic tetrameters because there are four feet in each lines; and each foot consists of two syllables; and in each foot the first syllable is light or unstressed however the second is stressed. There's also some versions, say the first foot of the first brand has a stressed syllable followed by an unstressed one; so it is trochaic; but it is natural to iambic, too. These variants have been written deliberately. In-line 4, there are three successive stressed syllables in what long love's times in order to emphasize the space of that time period which is mentioned in the words. Of course, a few of them are written limited to variety like lines 3, 5, 6, and so forth. There is a spondaic foot in-line 12 in Vaster probably to add significance to the word.