Guitar acting really wierd?

My Electric Guitar, when its plugged into the amp, only works when i touch the bolt on the pickup. I can hear it play on the amp but only a little sound. but then i put my wrist on the bolt and play i hear it enormously and great. ONLY when im touching the screw/bolt. im really confused and i really wanna play guitar. i tried putting metal things on it maybe itll play then but it only works when im touching the metal thing.