Does it matter if I store royal icing in a metal or a glass bowl? I don't want there to be some funky chemical reaction between the icing and the metal bowl.

Stainless steel is perfectly fine. Plastic is not a good container for royal.

I agree with JoAnn, glass or metal are way better than plastic.

I've used both metal and glass and found no difference. Do not use plastic.

I have used plastic but I washed it (again) using Dawn and HOT water and made sure it was squeaky clean (literally). I will work, you just have to make sure there is no grease.

I store mine in one of those hard plastic Rubbermaid no stain containers with no problems.

I also have a rubbermaid bowl designated for royal icing. Has only been used for this. Never had a problem. I do lay suran wrap down on surface first before closing lid.