system
Given the following post, respond as if you're commenting on Reddit:
human
How does cling-film (Saran-wrap) stick to itself? Does it leave any residue on the food?
gpt
Cling film easily builds up static electricity, the mechanical handling of it causes some electrons to get separated from their atoms, and so there's a charged imbalance causing an electrical force as the negatively charged electrons try to get back to their atoms. Since the cling film is an insulator, they can't just flow through the material. The same static electricity is also responsible for the general 'clingy-ness' of cling film. You may have noticed that cling-film sticks better to insulators like glass and plastic than it does to metal, which is a conductor which allows the static electricity to discharge easily. 

Cling film is pure polyethylene (PE) plastic. It doesn't leave any residue (unless you leave the film itself) and PE itself is non-toxic.