How to derust metal?

Could you please elaborate on the process of derusting metal? Are there specific methods or chemicals that are more effective than others? Also, is it necessary to take any precautions when working with these chemicals to avoid any harm to oneself or the environment? Furthermore, how can one determine if the rust has been completely removed and the metal is clean and ready for further use? Lastly, are there any long-term benefits to derusting metal, such as increased durability or resistance to future rusting?