A field must circulate. The MetabolicLoop names the cyclical process through which a corpus transforms external inputs into internal mass and expels waste: not as a linear pipeline, but as a closed system of continuous transformation. In biology, metabolism is the sum of all chemical processes that sustain life. In Socioplastics, it is the sum of all conceptual processes that sustain the field. The MetabolicLoop identifies the cycle: external concepts enter through the PortHypothesis, are processed through the field's internal grammar, are transformed into CamelTags, are integrated into the corpus, and eventually become obsolete, at which point they are archived or autophagized. This is not a metaphor. It is a structural homology. The field eats, digests, grows, and excretes. The MetabolicLoop makes this process explicit. It asks: what is the field's nutritional intake? What is its metabolic rate? What is its growth curve? What is its waste product? The answers determine the field's health. A field that eats too fast without digesting becomes bloated. A field that digests without growing becomes stagnant. A field that does not excrete becomes toxic. Node 2995 places this concept in Core VI because metabolism is the fundamental condition of executive operation. The field must sustain itself before it can act. Without this concept, growth is understood as expansion. With it, growth is understood as metabolism.