If you would like to make an explicit comparison of two dissimilar things without using like or as you would use a metaphor.
We consider a metaphor a figure of speech. It helps us to describe an object or an action to better understand it. Using metaphors is a good way to explain any sentence or idea. For instance, try to explain being in love. Well, that is when we use metaphor and say "love is like being in the clouds all day." And you perfectly understand what is to be in love.
Im assuming youre talking about a famous Frankenstein poem. He does so because he is desperate for a friend. The old man is blind so he feels that the monster is not much dIfferent from any human.
