Naturally the drawback to playing XME is that it's a little pricier than X or FCX , so it'll tie up more buying power, and the short calls are more "premium poor" than those in more volatile underlyings like X or FCX . The plus is that it's more of a shot gun approach to the entire sector ... .
Here's an example:
100 Shares XME at 16.23
March 18 17 short calls
Max Profit: $159 (if called away at $17)
As you can see, though, I have to go all the way out to March to get something north of a .50 credit for the short call (the March 18th 17 currently goes for a .83 ($83) credit per contract, so I'd probably only do this play if you're prepared to hold the position longer than usual or are looking for greater potential upside to the play. Naturally, you can do something shorter term (e.g., the Jan 15 17 short call) and see how things go ... .