Does it make sense to put a router into Bridge mode for the purposes of using it with a hardware firewall?

I have a fiberbox and a router. I want to put a hardware firewall in between the two, but when I power on the firewall, it doesn't have any WAN address, presumably because the modem isn't assigning it one (I'm new to networking so excuse errors). From what I've read, I need to enable IP-Passthrough or Bridge mode on the modem. I called my ISP, and they said they aren't able to do that, and I need to contact the manufacturer of my router and have Bridge mode enabled on it instead. Would this still be helpful in my situation? Is the idea that I'd put my Router into Bridge mode, connect it direct

Question by pushkin on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.