MGM was a programming block featuring cartoons from the MGM cartoon studio. These shorts were on Cartoon Network, but MGM was the first original series to air on Boomerang, from 2003 to June 1, 2014. This series is a collection of classic Metro-Goldwyn-Mayer cartoons from 1934 to 1958. It doesn't actually show Tom and Jerry or Spike and Tyke shorts from MGM, those are shown on the Tom and Jerry block. It also does not show Droopy shorts. Those have their own block as well.
Boomerang's Video-on-demand app does have several of these shorts for viewing.