The .m2ts file format is given to video/ audio files created by certain Sony Camcorder models. These files normally have a corresponding .modd file in the same location, which holds time-stamp information.

Sony Camcorders that produce this file should come bundled with software to convert the format to something more popular.

 Convert Sony Camcorder M2TS/ MTS video to MOV, MP4, 3GP, AVI, MKV, MPEG, ect on Mac, refer to this video converter for mac guide.

If you want to convert Sony Camcorder M2TS/ MTS video to MP3, M4A, WAV, AC3, MKA, etc. Refer to this video to audio converter for mac guide.

If you need to add movies to your website, publish them on YouTube, create versions for iPod, iPhone, and Apple TV, and play on iTunes, QuickTime, you have to import Sony Camcorder M2TS/ MTS video to iMovie first.
How to make a home movie on Mac using iMovie.