Figurative expressions have meaning (notwithstanding some who apparently think "figurative" often means "meaningless"). Note the structure of the three different expressions: the first term is (in I.A. Richards' terminology) the "tenor" -- the "principal subject of the metaphor"; the second term is the "vehicle" -- the "borrowed idea, or what the tenor resembles."
For example, in "The sun is a red balloon," the tenor is the sun and the vehicle is the balloon (i.e., characteristics of redness and roundness are being attributed to the sun).
Christ is like "bread of life," because He is life-sustaining; He is like a vine because life-giving "sap" flows from and through Him; "bread" and "vine" say something about Christ, illuminate one aspect.
In the words of consecration, conversely, if it were figurative, "My body" would be the vehicle and say something about "This" -- the bread (which would be the tenor). Note He does not say "My teaching", but "My body." What exactly do you think "body" illuminates about "This [bread]"?
There’s an important distinction in the Greek too. I am the “true” vine uses Greek alethinos, which is true by analogy, figuratively true. Now contrast that to John 6 where Christ says “my flesh is true food, and my blood true drink.” That “true” is alethes, which is true as to substance, real genuine, authentic.
In John 6:47-58 Jesus compared himself to the manna that the Israelites feed on to sustain their physical lives and yet died by saying he was the bread that if one fed on would not die.
How to “feed” on that “bread”? Vs. 47 says by exercising faith in Jesus and his sacrifice. As Paul said, Christ entered into a “holy place with his own blood”, into heaven.
Just as the physical bread sustained a person’s life that “bread from heaven”, Christ, would give everlasting life. The bread represented his flesh.