Lead flashing around chimney
 

Is lead flashing necessary around a chimney? Are cheaper, lighter materials sufficient?

Lead is traditional, but other forms of flashing should work.

These are IKO pictures, but GAF should have the same type of thing.
https://www.iko.com/na/learning-cent...to-install-it/

I expect aluminum may be a little cheaper, bu it's a small job, so the total dollar difference will not be huge.