Metal frames are made of different alloys, and the type of metal used affects the weight, durability, and look of the frame. Metal can be thin and barely-there, or chunky and bold.
Metal is strong, lightweight, and easy to adjust. The nose pads can be fully altered to fit every contour of your bridge, and if you bend a metal frame it will usually go back into shape. It can provoke a skin reaction if you have sensitivity to metals - if so ask for stainless steel or Titanium materials.
For women, traditional metals are larger and feature subtle detail such as engraving or inlaid colours on the side arms or trims. Designer metals copy the chunky geek plastic style, but in a slimmer rim format, with hot colours and minimal detail.
For men, this year's look is deep and square, with 1950's styling and the detail in subtle inlays and linings. Colours are much more subtle when applied to metal, so you could try deep blue with a flash of teal or even lime!