Jason, the process is exactly like repainting a car. Clean the surface really well as kitchen oils and greases plus oils from your hand don't let paint stick well, sand to roughen the old paint and fix any dents and other defects, prime, paint. Obviously it is better if you take them down to do it and it is much better if you spray paint. There is no reason that your cabinets can not look better than new.
You might want to search the board and the FAQ page since this has been answered in more detail several times before, but I didn't check the current status or location before I got too far into these comments.
Come back with any specific questions, though. Search the board by typing Ctrl-F and tyoing "metal cabinet" and variations into the space in the Window. They click and read the posts as they are highlighted.