Final answer:
Old English poetry, like that in 'Beowulf' and 'The Dream of the Rood', is characterized by its use of alliteration and a distinct metrical structure with a caesura separating each line into two halves.
Step-by-step explanation:
Old English poetry, as represented in works such as Beowulf and “The Dream of the Rood” (often referred to as “The Song of the Rod”), is primarily defined by its use of alliteration and its characteristic metrical structure, rather than rhyme and meter, free verse, sonnet form, or haiku structure. These poems employed a specific form of rhythm that involved the repetition of consonant sounds at the beginning of words in a line of poetry. Additionally, the poetry was typically written in lines that had a caesura, or pause, dividing each line into two halves, and each half-line would often have two stressed syllables, though the number of unstressed syllables could vary.