I had spinal stenosis surgery five years back with metal implants with screws, is above implants permanent or to be removed at later stage?

Permanent. Permant there if appropriately placed there comes to be no good reason to remove them their removal will not relieve backpain they can and should stay in.
Usually not. The instrumentation does not usually need to be removed.
Spinal Implants. Technically, the metal implants are no longer needed once the fusion has healed adequately. The reality is that we consider those implants to be permanent and there are relatively few reasons for removal. Pain attributed to the metal implants is often from other sources and the surgical approach for removal can sometimes itself result in different but new pain.