can i put my Apple Watch series 8 on my wrist that has metal plates and screws in it

Most plates are titanium and should not affect anything. You may have a problem if they are stainless steel with the compass.

You may also have problems with Assisted Touch where the watch picks up tendon movement to replace taps for people with limited ability on the opposite hand. Not many able bodied people use that.

You can also wear the Watch on your other wrist and change the orientation so that the crown remains facing your fingers (facing right for left handed use, facing left for right handed use)

I would see if you can try one at an Apple Store before buying as it is quite a rare thing to ask.

You have 14 days to send back the purchase for a refund, no questions asked, in most countries except India.

Of course you can, after all it is a piece of equipment designed with recycled materials of earth, totally safe and tested in labs with verified and licensed members of apple