When it comes to melon, there are a few key things to look out for that will help you determine if it has gone bad. First, take a look at the color of the melon. If it is starting to turn brown or black, then it is definitely past its prime and should be thrown out. Another telltale sign that a melon has gone bad is if it begins to emit an unpleasant odor. If the melon smells sour or rancid, then it is time to get rid of it. Finally, give the melon a gentle squeeze - if it feels mushy or slimy, then there is no doubt that it has gone bad and should not be consumed.