Rust is not a functional programming language :-) it has features which are ML-like, and it has first-class functions, but it doesn't really encourage functional idioms like the ML languages do.

If you want a great intro to ML-style statically typed functional programming (without the Haskell-style monads and functors jargon), check out https://www.coursera.org/learn/programming-languages/ . You'll get a lot out of even just going through the (10 minute each) lecture videos, Prof. Dan Grossman is a great explainer and it's a treat finding out the cool syntax, semantics and idioms of an ML language.