Though you should be able to make this work, I’d suggest a different approach. The state machine exists for this reason and I suggest you take a look at that. It’ll allow you to easily blend your various states with some simple rules, either based on button press or timing or whatever really, whatever is required to make it function like you need to.
So, the idea being that you use state machine to drive your base animations, moving around, idle, etc. On top of that you can then use montage to trigger specific unique animations, like an attack, for example. Again, though you probably can use purely montage, or even purely state machine to do it all, but it helps to use a combination of the two to make life easier. So you use what makes sense for that state.
If you’re set on using only montage, then you will need to really work out your combinations and how you trigger them… etc. With montage when you call an animation, it’ll play through and then stop. If it’s a loop, it’ll play that loop until you call another animation or stop the existing one. Without a state machine to fall back on, you’ll need to make sure you’re always calling some animation. Though I’ve never attempted this specifically, in theory you should be able to get what state machine allows you to do, but with much more effort and taking care that you cover all your bases.