If someone tells you they are playing Machine Head it could actually mean a couple of things as the deck archetype isn't set in stone, but one thing is certain and that is that it involves Juzam Djinns.
As there is no clear definition of Machine Head it is a little bit hard to write about but it usually involves big creatures like Erhnam Djinn and Juzam Djinn combined with Birds of Paradise to ramp into them. Other cards you usually see in this archetype are Dark Ritual and Elves of Deep Shadow for even more ramp.
It's also not unusual to splash a third color or maybe even two. First of all, you can splash red for Lightning Bolts and Sedge Trolls, or you can splash white to top the curve with Serra Angels and have access to white's amazing removal. Of course you can also splash blue for power, but that's about it.
Last but not least, on card you can play if you really want to hit the opponent hard is Berserk, some decks even play a complete playset.