You won't find any specific rhyme scheme or meter in "The Colossus." Plath doesn't pull any of those other typical poetic tricks like assonance or alliteration either. Instead, she uses free verse to deliver her striking imagery in an almost conversational tone. Sure, it's like you're hearing an incredibly smart and literate person have a conversation. We don't know too many people who'd casually drop words like "tumuli" (15) and "acanthine" (20) in a sentence. But still, the lack of any of those poetic formalities works well to make this blasted wasteland feel intimate and personal.