Robots aren't scary enough. We need to rectify this.
The basic principle of zombies as a monster of horror is that they represent the inescapability of human mortality. Zombies are slow, dreary, lurching, almost pathetic creatures which nevertheless inevitably overcome all obstacles and, one day, while you're asleep, will get you and remove your capability for life and turn you into one of them. In 28 Days Later they move at some furious speed which kind of defeats that metaphor, even if it does make them substantially scarier. That's the premise, though.
Vampires seem to have all kinds of clever superpowers and a hodgepodge of bizarre weaknesses. The precise items making up those two lists varies from canon to canon, but in most cases it's a bit of a mess. I've never really "got" vampires as a subject of any substantial interest, I don't see how they're supposed to be scary or threatening or interesting or noble. This opinion probably results from never having experienced much in the way of vampire fiction, but also, vice versa, so, whatever. Anyway (and this is an evaluation I've pretty much stolen from elsewhere, but I think it's logical), vampires represent fear of sex and intimacy.
Werewolves symbolise the dangerous, primal, animal nature of man which is just waiting to surface given the right trigger.
Aliens represent foreign people. Alien cultures hold the mirror up to humanity and show us ourselves.
As monsters, I hold that robots represent the threat of technology. Robots warn us that the human race supplanted more primitive ancestor species and that, one day, we, too, may be supplanted by our offspring. Robots are the fear of science advancing so far and so fast that we are left behind and then killed for not keeping up. Robots are smarter, faster and stronger than we can ever be.
Except for the "faster" bit. See: Cybermen, Terminators. (Aside: following Aliens and Predators, any bets on there being a movie entitled Terminators soon?) My basic observation is this: robots are metal, mechanical devices. As a result of our perception of mechanical devices in reality, robots are typically depicted as being slow and plodding, even if they are tremendously strong and typically bullet-proof. But robots, by their very nature, should be able to react infinitely faster and with infinitely greater precision of action than an ordinary human. It is consistent, both with logic and the metaphor, for robots to always move faster than the human eye can even follow.
It is not logically consistent for humans to be able to fight robots and win.
When a robot shoots at you, it does not miss. When you peek out of cover to see if the robot knows where you are, the robot shoots you instantly. When you run between cover to try to draw the robot's fire, the robot shoots you instantly. A robot does not have reaction times. A robot does not hesitate, it kills you.
A robot doesn't need to shoot you anyway. By sacrificing its heavy steel frame, armour and armaments for lightweight aerospace materials, my robot, while more vulnerable to physical damage, can move - on foot - faster than the human eye can see. That means it can get to you and punch a hole in your carotid artery - and the carotid arteries of all your closest friends - in the time that it takes you to realise that there is a robot cresting that hill over there. Maybe it uses a knife. Maybe it just kicks you in the throat with one sharpened toe at a hundred and fifty miles per hour.
A robot doesn't pause. A robot doesn't wait. A robot doesn't catch its breath. A robot doesn't stop to think, plan, plot or scheme. If it created a plan, you didn't notice, because the plan was created in a matter of milliseconds, while the robot was in motion towards your carotid artery.
You'll never see it, because it moves so fast - and keeping the monster hidden is one of the greatest principles of horror - but if you slow down the CCTV footage of my robot escaping the facility where it was constructed, you'll see that it looks emaciated, flimsy and whiplike, like a skeleton made of lightweight fibreglass reeds and car radio antennae, like the spider zombies from Ravenholm but with a belly full of battery and enormous freaky exposed binocular camera eyes. It moves at the speed of Rat Thing from Snow Crash. It doesn't move like a human or even like a regular creature but flails at the ground like some rabid monkey, some wild alien insect. Its electric battery - which can propel it at top speed through five carotid arteries per second for maybe a month and a half - buzzes angrily and loudly and is the only sign that the thing is approaching. "Approaching", not "nearby". The robot does not stand still for long enough to be "nearby". It's either coming towards you at high speed in order to kill you, or you're dead.
If we're still going with my personal vision, then I will add that the robot can't hear - the noisy buzzing battery would make that impossible. It can't speak, because it's not intelligent. And it can't learn or solve problems beyond basic pathfinding, because it's not intelligent.
Why is it not intelligent?
So it can't learn. Lucky you.
So how do the humans win? After all, the humans have to win.
A substantial number of independent - or, heaven forbid, cooperating - robots would shred a whole continent in a matter of weeks, but given a sufficient lead time, here is how you kill one:
Construct a very large static magnetic field and bait it so that the robot runs through the field at high speed. The movement of an electrical wire through a magnetic field induces a current in the wire. This fries the robot's CPU.
An electromagnetic pulse could also work, but would be infinitely more difficult to set up. A simple electromagnet can easily be constructed anywhere that there is cable and power.