Never combine bleach with developer in a metal bowl since bleach is corrosive and can harm or taint metal.
Use a plastic bowl or ceramic/glass bowl.
Unless you plan on using a bleach based cleanser specifically indicated for metals. Avoid using it on any kind of metal surfaces like stainless steel appliances, pots and cutlery.
Oh! Tip: Lightning Kit
The At Home Hair Bleach Kit is the perfect prelightening canvas for Semi Permanent Hair Color. Infused with bond-protecting Plex 2.Oh!, enriched with Argan Oil, and featuring Comfort Fragrance Technology, it offers a worry-free bleaching experience, creating the perfect canvas for our semi-permanent hair colors allowing you to embrace a spectrum of your dreams without fear.