Read this excerpt from THE ROBOT AND THE CAVE by Christopher Rowe
"This thing weighs a ton," said Stephanie, struggling not to drop the burden she shared with her uncle.
"He weighs sixty-eight pounds," said Steph's uncle. Uncle Guillermo always referred to the SER, or Submersible Exploratory Robot, as a "he." He motioned for Steph to stop and they carefully set the machine down, softly as a feather. "The trail is smoother from here. Let's power him up and let him walk the rest of the way himself."
What type of figurative language is "this thing weighs a ton"?