system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does touching tinfoil with your teeth, especially when you have fillings, hurt so much?
gpt
When your metal fillings meet tin foil, the body’s weak electrical impulses create a closed circuit and you have essentially form a weak battery.  Remove the foil and it stops.  You aren’t electrocuted but you will feel a slight buzzing.  Your fillings must be pretty close to the nerve in your tooth so that would explain the hurt.