What is your cage material? If it is a material that does not contain zinc or heavy metals, then it should be ok. If your cage bars have a "coating" on them over metals, you want to make extra sure that your bird is not chewing off the coating and swallowing it or chewing the metal on the bars.
Does he have a particular spot that he likes to climb and gnaw? You could try covering that spot with a big toy. I would also put some spray millet or parsley leaves hanging from that area of the cage. He might like chewing on those more than the bars.
Bethany and Jorge
Mini schnauzer, Watson (July 18, 2009)
Budgie, Sammy (April 13, 2014)
RIP Príncipe Pío