Max has PTSD. The way his character acts, the things he said, all resonated strongly with me: everyone with PTSD acts differently of course, but I was able to relate to Max so much throughout the film. It was pretty great because the day I saw this movie, I had been sitting at home suffering myself, and a friend came over and coaxed me out of the house. I thought it was going to be cars and guns, but wow, was I wrong. And for a sufferer of PTSD, there were also two beautifully symbolic moments that are still touching to me several days later....here's my addition to why this is a hidden masterpiece of film.
So, the first bit of symbolism: Flashbacks
Even in the opening sequence of the movie, he is blatantly suffering from flashbacks. He states in the narrative "Here they come again... worming their way into the black matter of my brain. I tell myself, they cannot touch me. They are long dead." There's a vision of a child that seems to be attacking him, or trying to get his attention. He reacts in your standard fight-or-flight way: terror, horror, striking out. In one scene he's sleeping and wakes up with a raised fist...I've done that exact thing before, and even punched before I fully woke up.
Anyway, you get used to seeing Max be jumpy and on edge through the entire first hour of the movie. The vision appears at really random times and he is always sweaty, nervous, and looking around in fright before he realizes there's no one there. But then during the big epic finale battle, he's fighting off hordes of the War Boys et al, and at the same time as one charges at him with some projectile launcher, he has another flashback. Max reacts to the flashback, not the current situation, shielding his face with his hand from the hallucination.
Right at that moment, the War Boy shot a dart right at his face. Instead of the dart going into his eye or brain, he actually blocked the fatal blow with his hand, and the dart embedded in his palm. It's a pretty grisly scene where probably everyone else in the theatre went "Cool!" or "Gross!" If you look at the symbolism there though, Max was the actualization of the entire purpose this debilitating condition; life preservation.
PTSD is all about the threat of death, the fear of your well-being. We do what we do because we feel threatened, and not "am I going to get jipped on my whipped cream on my frappucino" threatened. And it's hard, and we feel bad, and maladjusted, and like we're weird assholes, because we are reacting to a situation that 1) isn't even real or a threat to us anymore, and 2) we are very, very afraid. To see his reaction actually save his life was a very subtle reminder of the reasoning behind our fear. It was taking the perceived negative of PTSD and showing us that it is powerful, and can be positive. I know that's a shitty thing to say to anyone with an illness, but it's true.
Second bit of symbolism: Max walking away
The movie has a happy ending, everybody's celebrating, water is running down the hills and the warlord is no more. It's pretty inspirational and gratifying to see thousands of happy and grateful people all in celebration. They're literally now in paradise, if only for a few minutes.
And then you see Max.
He nods a goodbye to Furiosa and departs into the crowd, quietly. A lot of people are misinterpreting this, but again I found myself relating to it all too well. PTSD makes you look over your shoulder, tells you to keep moving. Tells you you're not safe, or that there's more work to be done, more distance to put between you and Hell. I always envy the ease with which other people slip into comfort, even with normal day-to-day relationships and activities. I don't really have that luxury a lot of the time.
So in other words, where others can stop and have a break, relax and say cheers, we're doing exactly like Max. Looking for the exit, or hoping to find a "safer" place or person or time. It was so wonderfully executed and just like the other symbolic nod to trauma and its effects on us, easy to miss, unless you're unlucky enough to be mad, like Max.