As I was idly paging through the comments thinking about how many of them were jumping to outlandish, unsubstantiated conclusions about why the poor submitter was being asked to come up with metrics, I also realized that pretty much nobody (in the finest tradition of Slashdot) has bothered to answer the actual question: "I'm wondering what people opinions are on what good metrics should be in regards to mttr mtbf etc." I think I misunderstood this at first as well... in light of what he does say about the goals ("...determining if we are performing above or below what is considered optimal") I don't think he's asking what metrics to measure or whether or not we think doing so is any good, but instead what reliable industry benchmarks are for those metrics, so he can tell his boss what is "optimal" or not about their operation.
Well, shibby, sorry, but I don't think there are such things, or at least none relevant enough to take back to your management team. The only way to get anything meaningful out of metrics (obviously a lot of other posters are arguing you'll get nothing meaningful out of them; I disagree, but it may not matter either way if those are your orders) is to establish baselines for your organization and track future performance against those. It will take a while and it will have to be viewed in context to be worthwhile... important points to make when you are presenting your findings to management.
I'm being optimistic and assuming genuine business goals and a desire to understand IT operations on the part of non-technical managers are the point of this request, not some haphazard effort to chop down a three-person department, but it is also worth passing along some of the critiques that are being posted here. On the other hand, if you don't already, you should understand that not all managers are buggers, and that many of the better ones have legitimate reasons for trying to understand what is going on in their IT department. We often forget how mysterious what we do looks to the un-initiated, and I have seen enough poorly run IT departments to sympathize with non-technical managers who are grasping for the tools to understand theirs. The point being, getting defensive and obstructive in the face of these requests isn't always the brightest idea; instead, you can look at it as an opportunity to present some of your perspectives and difficulties to managers who are finally prepared to hear about them (after all, they did ask!). They may not have the time or horsepower to learn everything you do in depth, but it is possible to analyze operations based on the right sort of shorthand.
The cynics may be right; only you will know. But I've seen companies run down by their IT departments as often as I've seen IT departments run down by the management team, so performance concerns on both sides are well-founded. Anyone who thinks their manager shouldn't ask for a suitably abstracted toolset for judging performance is asking for a stupid manager.