Antimatter is a very good source of energy. Then Antimatter comes in contact with Matter, there is almost instant Annihilation. This Instant annihilation is caused because the particles of Antimatter 'Cancel Out' the particles of Matter.
For Example: When A Hydrogen Atom reacts with an Anti-Hydrogen Atom, the proton cancels out the AntiProton, since they are oppositely charged. Meanwhile the same happens with the Electron and the Positron (Anti-Electron). This happens because when a Positive proton and a negative Anti-Proton attract each other, the charges become neutral, thus releasing all the energy within. So the particles are completely converted into Energy.
In the Future, man might
be able to harness this energy, which is much more powerful than a Neuclear
bomb explosion. This source of energy is also one of the most expensive. Millions
of dollars go into making a gram of Antimatter, and it is also a very slow process.
So, we just have to wait for the future!