The Higgs boson is now a part of the standard model of particles. There may in fact be others. I tend to think that dark matter is weakly interacting massive particles. They cluster and attract normal matter gravitationally, but pass through normal matter like it’s not even there. The room you’re sitting in could be filled with the stuff but impossible to detect by any conventional means.
Okay. Gravity is as yet unseen. So is dark matter. How does gravity work, and attract normal matter? Check out this article:
http://news.vanderbilt.edu/2013/06/dark-matter/
“… the physicists propose that dark matter, an invisible form of matter that makes up 85 percent of the all the matter in the universe, may be made out of a type of basic particle called the Majorana fermion. The particle’s existence was predicted in the 1930’s but has stubbornly resisted detection.
A number of physicists have suggested that dark matter is made from Majorana particles, but Scherrer and Ho have performed detailed calculations that demonstrate that these particles are uniquely suited to possess a rare, donut-shaped type of electromagnetic field called an anapole. This field gives them properties that differ from those of particles that possess the more common fields possessing two poles (north and south, positive and negative) and explains why they are so difficult to detect.”
“… Scientists hypothesize that dark matter cannot be seen in telescopes because it does not interact very strongly with light and other electromagnetic radiation. In fact, astronomical observations have basically ruled out the possibility that dark matter particles carry electrical charges.”
There’s a lot of work being done over the last fifty years trying to figure out this stuff. A lot has been written. Einstein couldn’t figure it out. But a breakthrough could be imminent (I hope).