My understanding is that Rust lacks the ability to have a generic Monad abstraction like Haskell and Scala, but that it certainly has monads (e.g Option, Result

My understanding is that Rust lacks the ability to have a generic Monad abstraction like Haskell and Scala, but that it certainly has monads (e.g Option, Result, Vec, etc). And indeed that even languages like JavaScript have lots of monads (e.g. Promise) it's just that these are likewise not abstractable. I believe that a monad is basically any container that has both a constructor and a flat_map function (and there may be one other requirement that I've forgotten). The special ability that Haskell has is the ability to write code that is generic over any such container.