Rob check out this link it will explain a lot. Not sure who sales metal roofing in your area but this company is big around these parts.
http://www.muellerinc.com/roofing/index.phpThere are many more as well. As for your question standing seam is designed so that no hardware is seen or exposed. Each sheet interlocks with the next and covers the screws holding it. Standing seam material is generally sold in rolls and is brought on site and cut and formed on the job site with a special machine. The other metal roofing systems have various cross sections you can go with. The sheets can be purchased pre cut to specific lengths. As Bski noted you can get the metal in galvalume or painted. Painted is almost double the cost of galvalume I belief haven't purchased any in several years. Mueller’s has a product called AP panel it emulates standing seam but like all the others it uses screws with rubber washers which are exposed. It is what is on my house & my relatives house you can see it in the pic's I posted. Ap panel and standing seam all have to be placed on a solid deck were as the other types H and R panel can be placed on lath strips because of the way it is formed it can support it’s self across a given span.
