It’s a balloon.
Last week I watched an episode of the show "True Paranormal: Fact or Faked." During the episode, they decided to try to debunk a video some guy took of what he claimed was a UFO. They ordered a balloon that looked like the UFO in the video, filled it with helium and let it go, and filmed it flying around. It looked exactly like the UFO in the video. It even caught the light just the right way so it looked metallic. They also contacted the local police to see if anyone else had reported seeing the UFO the same night the guy filmed it, and one of their police officers saw it, and verified that the UFO was actually a balloon that looked like a flying saucer.