What is standing seam metal roofing?

There are two important terms that will help you understand standing seam metal roofing. (Keep in mind that there are other options than "standing seam."  Options include metal roof designs that have the appearance of "traditional" roofing materials.)

First is standing seam.  The standing seam is the "bump" in the metal panel at the end that overlaps the adjacent panel to connect the two panels  There are dozens of ways this connection can take place, and many are exclusive to individual makers.

The "profile" of standing seam metal roofing refers to the "bumps" in the metal sheet.  How many are there in each panel?  How far apart are they?  How high are they?  Again, many profiles are unique to a specific manufacturer.  The profile also depends on the end use, such as - in non-commercial applications - the distance between the rafters.

Do metal roofs expand and contract?

Metal expands and contracts as it warms and cools. Most new metal roofing products have fastening systems that accommodate movement.