يَكُونُ وَجْهُ الشَّبَهِ شَامِلًا لِلطَّرَفَيْنِ
The ground of resemblance should extend to both sides.
Calling a courageous person a lion works because bravery can serve as a fitting shared quality. If the chosen property has no coherent connection with the familiar image of a lion, the comparison becomes weak.
Shared resemblance does not mean that the subject and the borrowed image are literally identical or alike in every property. It means that the specific feature intended by the expression is relevant to both.