A poet might choose to make some longer lines, called hypermetric lines. In them, the first half-line is preceded by an extra lift and dip(...) and the second by a dip(...). These lines do not occur by themselves, but in groups a few lines long, like this one from the poem Beowulf, lines 1160-1164.
...Bearers offeredWhy the old poets used hypermetric lines, I cannot say, but you might find a use for them to slow up the action or add a little variety.
wíne from | wóndrous containers. || And then | Wealtheow entered,
góing in | a gólden tórc || to where | the twó góod ones
ídled | úncle and néphew || without | émnity yét,
éach one | trúe to the óther....