Can I bake small pieces of chicken in the oven on a metal bake sheet? Or would glassware be better? When I say small, I mean 1/2 inch pieces
yes, you can cook small pieces in the oven. If you're cooking a whole panful, a greased metal pan would likely be best (or greased chicken on your metal pan, whichever). When I'm cooking just a few pieces of something, one person's worth, I'll sometimes just pop them on the baking stone or even just on the rack - though your tolerance for such shortcuts may vary.
For such small pieces, they'll likely cook pretty quickly, so you might want to consider that when choosing how to cook them, though. If you pan is large enough for them to be fairly spaced out, I would suggest preheating your oven well, and turning it off as soon as the chicken is placed inside - they will cook in residual heat, and the cooking will be both a bit slower (less likely to overshoot) and less direct (less likely to cook unevenly, say, burned on top). Of course, if you're cooking enough to crowd the whole pan, you might want to adjust your cooking method suitably.