You can take Ipod's on board, and use them during the flight, but NOT have them on for taxi-ing (moving towards the runway), take off, and landing.
Other than that, they are fine.
I have never yet had my gold earrings, necklace and rings set off the machine, unless there is a high alert, the machine setting is not set to pick them up.
However, If you have a really big bulky metal watch or bracelet, it might do.
Also, if you have any piercings in any "personal" places, you might want to takt them out for the journey. They may not set it off, but if something else makes it beep, they use a hand scanner, which will beep as they move it over you.... so everyone in the Queue will know exactly what you have!! Can be a little embarassing!