what do you mean by metal? Like wire? or metallic beads???

Wire would probably not be a good idea, seeing as how it could break and end up poking you while you slept...but ye, the metal clamp beads are pretty easy to find...

I'd not colour your hair with metal bits in it, tho...all hair colours tell you not to let the solution come in contact with metal...it could do anything from starting to smoke, turn green, or even eat thru your hair...

Ear cuffs work great.

Metal wire would work just fine. (I'd recommend grabbing a dowel around the size of your dreads and some cheap jewelry pliers and trying your hand at all sorts of fun coily designs if you're feeling creative. That way you can slip them on and of for dying.) You can use really any type of metal you want, but remember that repeated washings and dunks in water will do weird thing to some metals. If you're feeling fancy you can always try sterling silver wire. That will hold up really well.

And like David said, ear cuffs are always a great bet too.

Just remember, you don't really want to keep wraps and beads in one place on newer dreads cause you want ot give the hairs room to move around and lock up, so something movable/removable is probably the best way to go.