YOU might not have to bond that metal to your spa, I did because that part of the NEC is enforced by the local inspector in this area.
If the electrical service to your spa was installed by a professional who pulled permits and got the required inspections, your installation was probably done to code, and I wouldn't worry about it.
If it was done by yourselves, or a handyman, or anyone who didn't pull the permits and get the inspections, then it's anyones guess if your install is to code.
Like I said, what is code now wasn't code 4 years ago, and what and how the code is enforced may differ in your area vs where I live.
If you're at all concerned- you could contact your local inspectors and ask them. But be prepared to correct anything that is out of standards in the event they come for a visit. On your dime.
