So how does “This My Body” function as a metaphor? What does the “My Body” illuminate about the bread? Because the sentence is about the bread.
Gestural metaphors just work that way. If you know what I mean when I show you my daughter’s picture, and say “This is my little angel,” then you should be easily able to solve what Jesus is saying. The bread is the metaphor, and His body is the topic, the thing the bread is teaching about. As the bread is broken, so His body will be, for us. As the wine is poured out, so His blood will be, for us. These are remembrances of His death on our behalf. This is the Gospel in a picture. The meaning could not be more clear.
Peace,
SR