Computer Graphics Metafile (CGM) is free, platform-independent, international standard metafile format for storing and exchanging vector graphics (2D), raster graphics, and text. CGM uses an object-oriented approach and many function provisions for image production. CGM uses these object-oriented characteristics for remolding graphical elements to render an image. A metafile contains necessary information that defines other files. In CGM, a text-based source file contains all graphical elements that can be later compiled into a binary file.
PNG, Portable Network Graphics, refers to a type of raster image file format that use loseless compression. This file format was created as a replacement of Graphics Interchange Format (GIF) and has no copyright limitations. However, PNG file format does not support animations. PNG file format supports loseless image compression that makes it popular among its users. With the passage of time, PNG has evolved as one of the mostly used image file format.
You can also convert CGM into many other file formats. Please see the complete list below.