But in Hebrew poetry the rhythm may be in terms of units per line.
However, the exact nature of this is still debated and some recent scholars have concluded that the Psalms are not metrical, that this is an idea imported from Western poetical forms.
A second common characteristic of Hebrew poetry is its use of imagery, comparing one thing to another.
Of course, imagery can be found in prose sections of the Old Testament and it is not found in every psalm, but it is especially rich in Hebrew poetry.
The Psalms are meant to be sung -- and accompanied by musical instruments.