The first time I ever flew was when I was 16. Best. Experience. Ever! Everybody was so friendly! Free drinks, they let me keep my ipod on during take off so I could record take off. Very nice. Once I got off I had several people, passengers, flight attendants and even the pilots approach me ans ask me if I was satisfied with my first flight ever. It was VERY fun. Turbulence and the sharp turn while landing was amazingly fun, made me giggle. LOL
Don't worry about the metal in your wrist, just tell security in case the metal detector beeps you, you should be fine. My mom has a pace maker so she couldn't even go thru the detector, they had to pat her down.
TSA.gov has excellent information on what you can and cannot bring in your carry on. Remember the 3-1-1 rule! :) It saved my butt.
I wouldn't wear jewelry or belts. And wear flip flops, sandals or any other kid of slip on shoes, then change into sneakers after you pass security. That's what I did.
Take off and landing is fun! Take off is loud, and the pressure pins you back. Your ears pop like crazy too! Bring gum if this bothers you, but it didn't with me. Landing also pops your ears, and it's very fun as well.
If I were you I'd bring an iPod or a laptop with you to watch movies, listen to music, catch up on music/school. Some planes have wi-fi (domestic flights only), but many do not. Make sure you put your phone on airplane mode or turn it off too! :)
Have fun! I really enjoyed my first time flying, I can't wait to fly again.