It came with both - I've previously only used metal but now that I have a glass one too I'm curious if each is better suited for certain things.
Are you channeling your best self with this comment? (If you're not sure, check out our Code of Conduct.)
I like to use the glass one for bread dough as you can see how much the dough has risen during the rest time. Metal works best for chiffon or anything whipped.