As far as the difference between an allegory and metaphor is worried, equally seem to belong to the same group of figures of speech. The explanation is equally necessarily mean comparison. In his e book In Other Footwear: Songs, Metaphor, Empathy, Existence Kendall Walton also places the formulation of metaphors https://metafora53186.salesmanwiki.com/9610875/5_simple_statements_about_metafora_explained