He was a 10-ton block of steel when it came to action and getting up to get things going.
Metaphors are basically comparisons of things that are unlike. Metaphors are used, mainly, to give readers a sense of understanding when there may not otherwise be one. What this means is that authors will compare something that may not be known to readers to something that most likely will be known in order to present the best image understood by the most readers. If, for instance, you had a friend who was stubborn and wanted to convey just how stubborn this person is to readers you might say something like “He was a 10-ton block of steel when it came to action and getting up to get things going.” Thus, because only you would know for certain just how stubborn your friend is in certain situations, one way to communicate just how stubborn this person is would be to mention something like 10 tons of steel because everybody is familiar with how heavy a ton is—non moveable—and everyone will know what steel is. As such, metaphors can be used to communicate something by addressing a common point of knowledge.