A simile explicitly says that one thing resembles another; a strong metaphor suppresses that marker and presents the subject under the very name of its counterpart. This is often described as treating the comparison as if forgotten.
“This man resembles a lion” differs in force from “This lion is leading our group.” The latter foregrounds the praised trait through identification.
Such intensity still depends on an apt resemblance and a clear contextual cue; without these, emphasis may become ambiguity.