Let me try my hand at simply explaining this.
Atoms are composed to two sections:
A positively charged center -- the nucleus.
A negatively charged outside -- the electron cloud.
When several atoms get together, they do so because their electron clouds start intermingling. This sharing of their electrons is fundamentally what a bond is.
A bond is strong when both of the atoms really want their electrons to intermingle. Conversely, a weak bond is when the atoms are "forced" to be next to each other and intermingle. Strong bond = opposite poles of a magnet next to each other. Weak bond = similar poles of a magnet next to each other.
Somewhat counterintuitively, it's not the fact that the bond's want to separate from each other that makes something really explosive/reactive.
To really understand what's going on, you have to take a look at the energetics (thermodynamics) of how a reaction proceeds. The tendency of the physical world is always towards disorder (entropy). Rather than becoming more ordered, every single atom in the universe wants to be more comfortable.
Think back to our magnet analogy. Magnets with the same pole facing each other really don't want to be next to each other. In fact, they'd LOVE to find another magnet with the opposite pole facing them. The magnets which have a weak bond find it really, really easy to separate. In fact, almost anything will split the connection. However, those magnets, once separated, must find another (opposite) partner for them to pair up with. The amount of energy that they release when they find their perfect mate is evidenced by the fact that the magnets will literally hop across short distances and smack together in a satisfying *crack.
What we also know in thermodynamics is that energy cannot be created, nor destroyed. Thus the net energy in any reaction must be equal on both sides. We know a couple of things:
The energy required to split the weak bond is really, really little.
The energy released when a strong bond is formed is a lot (in fact, you hear the release of energy in the form of heat and sound!).
Atoms prefer strong bonds to weak ones (entropy).
Putting everything together, when you have an molecule with extremely weak bonds (HOOOH), it takes almost no effort for those bonds to come apart. However, when those oxygens go find other molecules to bond with, that releases some energy. Thus NET ENERGY is heavily favored in the exothermic (release of energy) direction. When enough of those super weak bonds are broken, and when enough of the strong bonds are formed rapidly, you have a simultaneous release of a huge amount of heat --- an explosion.
Sorry if that's a little long, but I tried to explain your questions. (Which was a fundamentally very interesting question!)