I was thinking about this kinda stuff before, and confused myself quite a bit
I was thinking, perhaps matter isn't really something in itself, but rather a lack of something, a lack of anti-matter. With magnetic charges it seems that if you can truly combine them you get a neutral charge, things can react to a positive, or negative charge, but if you combine the two and form a neutral charge? Matter must be the same way, when you combine it with anti-matter neither gets destroyed. They combine into a neutral form, and still exist, but things don't react to them... It takes energy to seperate the two (like oppositely charged magnets), when they're recombined that energy would be re-released.