What can max do?
It might not appear to be a proper "programming language". Usually we think of pages of text code.
Max is based on code like this, but hides it inside graphical objects. By moving around and linking these objects together you are designing the workflow of your max program.
Max blurs the line between "application" that you use, and "programming language" that is used to write applications.
Somewhere between the two. Max is an environment or application for programming.
What can it do? This question is like asking what can you do with photoshop? It's more useful to ask what is max good at. It's not good at everything. Technically max can do anything you want it to, but it's particularly good at some things.
Max is very good at dealing with input data of all kinds, and having that data affect output.
Max's interface makes "sketching" ideas very quick and fun. It's patch layout serves not only as the programs logic, but as a mental map or diagram of what it does. You can sometimes tell basically how a patch works from across the room (try that with text based code).
Max is good at making performative applications where many things are adjustable in real-time.
Max is good at "mapping things to stuff".
Max is creative and highly flexible, fast and fun to work in.
This does not necessarily mean it's easy to learn.