Dark Matter!!

[Manolo Sobrino]

ahem... Namir.... no...

Let me recommend you an easy and pleasant to read introductory textbook on elementary particles:

Introduction to Elementary Particles -
David Griffiths

There you can find that yes, the interaction via coupling to discrete charges is how you do these things, there are deep reasons for that, and no, states are not something you fill with mass or anything like that (it would be even better to get to know some quantum mechanics.)

For the moment, just don't worry about dark matter and please forget everything you've ever heard, thought, or think you know about parallel universes. Popular science sometimes causes harm... a lot of it.