Well, if you're focusing on ballads, that's a specific form and tradition of writing, so one of the easiest approaches is to look at how the poem is an example of a ballad and what that means. For example, the form of the poem is very regular, with a steady rhyme. Is that appropriate for a poem about madness and violence? What relationship does the regularity of the form have to the intense emotions felt? Do the form and emotions fit well together—or are they in conflict? If they conflict, where and how?
You could also look at the topic (murder, madness) and explain how that relates to older ballads.