The right arm was broken three years ago and the steel plate was not taken out. Can I go to the gym to work out?

To tell the truth, you'd better consult your doctor about this problem. I suggest you check the weight of your arm bones. Generally, you can slowly gain weight and resume exercise. You can put something like elastic hand protectors on the outside of the fracture site, so that the muscles can bear some inward pressure and ensure the effect of muscle protecting bones during exercise. However, before you start the heavy-weight exercise stage, you'd better ask the orthopedic surgeon in advance and give you some suggestions based on your situation, otherwise you won't practice well, and it will be even worse if you practice.