Hollow Metal doors and frames get specified in many commercial and industrial buildings (probably because the steel holds up better than wood). The website for Republic Door illustrates the many options available for hollow metal products. This excellent website will give you more information about hollow metal doors and frames than you should ever need.
In recent years, I've been using hollow metal frames with pre-finished wood doors in many buildings. The hollow metal frames provides a durable way to complete the gypsum board openings and the pre-finished wood doors are attractive and economical. The Mohawk Doors seem to be common. Wood frames, using wood trim boards around a wood jamb and header, are also popular. Wood frames tend to be site built, except for pre-hung wood doors.
Aluminum and glass storefront also gets used often in commercial buildings. I've installed more Kawneer systems than any other type, but there are lots of good manufacturers. Be careful to check the shop drawings on storefront, verifying rough opening sizes and the details of the frames. Pay particular attention to the fastener location in the frame and where it will fall in your wall. Many times, particularly in cavity wall construction, fasteners fall in the cavity area and extra blocking is required or the frames need to slide in or out of the opening to catch something on which to connect. This is never a pleasant surprise if it becomes apparent only as installation begins.