Qur’anic expression displays general rhetorical beauty, approximate sonic correspondences, and persuasive meaning that engage both hearing and understanding. A verse can be beautifully balanced without belonging to an established poetic metre.
Eloquence is not produced simply by extending a sentence or repeating one sound. At times brevity is more fitting; at other times a longer passage is required. Suitable placement, a natural ending, and the force of the meaning work together.
Important conclusion: freedom from one predetermined metre or rhyme is not a defect. It allows changes in sound to suit the changing rhetorical needs of the discourse.