How do I breed a Gold dragon?
From the DragonVale Wikia:
To breed a Gold Dragon, it has been established that the elements metal and fire must be present. This means many combinations are possible. The Gold Dragon can be bred at either the Breeding Cave/Epic Breeding Island.
It goes on to say that the breeding time is 48 hours, or 38 hours and 24 minutes in an upgraded Breeding Cave/Island.
You must, however, be at least Level 17 before you are able to breed the Gold dragon.
Note: Level 17 is your required level, not the required level of your dragons.