i Register
In some senses, enthusiast is marked as archaic. Watch for register when choosing this word.
noun
A person filled with or guided by enthusiasm.
But Charles Aubyn (for it was he) had, like most enthusiasts, overcalculated the influence of his eloquence; surprise had alone procured him a hearing, and the bold cavaliers around were little in the mood for a homily.
I would challenge any rock enthusiast to refrain from tapping his/her foot when listening to such music.
A person exhibiting over-zealous religious fervour.