In SAP, SAP MM is one of the core modules of the logistic process. So, one can definitely conclude that it'll be equally in demand in the future as well. It would be better if you have the knowledge of emw, am and other modules to succeed as a function consultant. As many companies are looking for candidates with implementation experience.
Want to learn SAP MM from scratch! Here's the right video for you:
If you are more into reading, then do check out this material provided by Intellipaat:
So I would suggest you join an organization where you can get the experience or shadow as a senior consultant during implementation.