The CMT file extension is related to e-Sword, a feature rich and user friendly bible software from Rick Meyers. A *.cmt file contains commentary data for e-Sword version 8.x and lower. The latest version of e-Sword uses the CMTX file extension instead.
The CMT file extension is also used for a digital image (RAW) format recorded by Chinon ES-1000 digital camera. One of the many RAW formats.