The OS is in between the service and the bare metal. Something like OPNsense can be said to be running on bare metal because the OS and the firewall service are so intertwined. However, something like firewalld isn’t running on the bare metal because it’s just a service of the operating system.

That’s how I understand it anyway, I’m not a pro

I’m all-in on trying to ratfuck Trump so I’ll be voting in the ® primary