Haskell isn’t the best venue for learning currying, monads, or other category-theoretic concepts because Hask is not a category. Additionally, the community carries lots of incorrect and harmful memes. OCaml is a better choice; its types don’t yield a category, but ML-style modules certainly do!

@[email protected] and @[email protected] are oversimplifying; a monad is a kind of algebra carried by some endofunctor. All endofunctors are chainable and have return values; what distinguishes a monad is a particular signature along with some algebraic laws that allow for refactoring inside of monad operations. Languages like Haskell don’t have algebraic laws; for a Haskell-like example of such laws, check out 1lab’s Cat.Diagram.Monad in Agda.