“Caged Bird” uses an extended metaphor throughout the poem. Even though you might not know what is being compared, how is the caged bird described? Compare and contrast the life of the caged bird versus the life of the free bird.

that's conceptually impossible.

if i wrote it, it wouldn't be a 'shakespeare' sonnet.

martians or other types of aliens represent a unique fear as opposed to zombies. vampires and other types of monsters.   in most sci-fi stories, aliens come from other worlds and have different or more advanced technology.   abductions and experimentation on human bodies that involve these technologies, or the use of these technologies against human beings and the use of unknown "powers", are a type of fear that's different from that of other types of monsters.