3ds Max Modeling :: Automatically Mirror Object?

I wanted to start learning how to use 3DSMax by first making a sword model that could later be used for a game like Skyrim. But rather than making some simplistic, blocky sword, I wanted to jump to something more complicated to speed up the learning curve.
 
I was editing existing models in Blender before, so I already know more or less how to operate a program like this, and everything else can be covered with tutorials. But there's one thing I can't find a tutorial for...
 
Let me explain it on an example. I want to make a model of this sword:
 
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The idea is that it's symmetrical and identical on both sides. I saw somewhere a video where a guy was somehow creating a model, and while he was working on one half, the other half was automatically updating and creating a perfectly symmetrical shape.
 
For this sword, I would be basically making only 1/4 of the sword, while the rest would be appropriately placed mirrors. I want this process of mirroring to happen automatically. How do I do that?