Why don't Christians cut off their hands after they have sinned? The Bible says you should?

I believe this is a metaphor. I studied this at school a few years ago and I believe it means that if your hand has caused you to sin, cut it off. For example if I cause you to sin you should cut me out of your life. It is not meant to be taken literally just a metaphor. The Bible has many metaphors, one verse can have over a 100 meanings.