Yes. "A value in a box" is more like a metaphor for a functor. The key part about monads is that you can "merge the boxes" (to strain the analogy). Or, as I'd

Yes. "A value in a box" is more like a metaphor for a functor. The key part about monads is that you can "merge the boxes" (to strain the analogy). Or, as I'd prefer to think about it, to merge different effects.