Flame Decorations Are There Metals That Put Out Fumes When Heated Slowly For A Long Time? Any I Should Avoid?

Are there metals that put out fumes when heated slowly for a long time? Any I should avoid? - flame decorations

I have closed a wood stove and I use metal on metal jewelry. They are not exposed to a flame, gradually but remain hot and hot.
And I know that some of them change color, in particular, I noticed a change in the color of copper, but I like change. I do not want toxic fumes.
To live well and do good.