metaphor
A metaphor is a comparison between two things without using like or as. In these lines, Romeo is saying that his soul is a soul of lead. This is not true. He does not actually have a soul of lead. He is just saying that his heart and soul is so heavy that he can't move.
An allusion is a reference to another literary work. There is no reference to anything else. A simile is a comparison between two things using like or as. There is no like or as. A pun is a play on words. While Shakespeare is known for using many puns in humorous situations, these lines do not have any.