The metal is smooth, but not shiny. It is super bendable. As soon as I realized what it was, I stopped handling it and washed my hands.
Lead is heavy, but seems such an odd choice for a weight in a consumer device. It must have been cheaper or even free.
Definitely not like any EMF shield I’ve ever seen. It’s definitely a very soft metal.
Did the battery have pull tabs at all? It could also be there to hold the battery in place if there were none. That isn’t uncommon either.
It had a strip of double stick tape under it.
Ok yeah so that sounds like a mounting bracket for the battery itself. That’s normal, probably not lead.
Genuine Apple batteries will have a pull tab for safely removing the battery, this appears to be a less sexy version of that.