In the first clip after the intro of this video, we see what seems to be some Russian fishermen who caught a fish and have placed a can next to its mouth. The fish proceeds to bite the can and take off full pieces of the can as if it was a cracker.
This represents the strength and sharpness of the fish’s teeth but also how cruel some humans can be towards other species. The metal in the can could definitely harm the fish if he digests too much, and in the video we see him keep making the fish take more and more bites.
It is somewhat interesting to see how the fish can crush anything it puts its mouth on, but in this case IT being a can is not very cool and pretty harmful at that.