Ok, I have installed a bulb and I put the chrome bracket back on to secure the light back to the bike. Does the little screw on the bottom that tightens the chrome around the light usually tighten all the way together? I have a small gap?

Also, what is the big metal thing that goes over the bulb for? Looks like it just spreads out your light. Do you need it?

 

The gap is probably okay... if everything is tight?
Sounds like you might have a Street Bob?
I don't have a clue about the big metal thing that goes over the bulb... neither of mine has one.

 

Whatever it is just put it back. It sounds like a diffuser or deflector. Maybe it keeps light from blinding other drivers.

 

The metal thing is the diffuser. If there's a slight gap, but everything is tight, then you're okay. Did you take a photo of the light housing with your digital camera for a reference point before you started? If so, take a look at it. If not, make sure to take "before" photos next time.

 

I just put a new bulb in. The gap is very slight. Use some blue thread locker to prevent it from coming loose, put the metal shield thing back, It is a light diffuser for the headlight bulb.