But yeah, so I was reading the wiki article about the tin man (called "The Tin Woodman"). In the book, the tin man started out as an actual human man named Nick Chopper. He was in love with a munchkin woman named Nimmie Amee who was a slave to the Wicked Witch of the East. To prevent them from getting married, the Wicked Witch of the East put a spell on Nick Chopper's axe that caused it to chop off his own limbs, one by one. The tinsmith, Ku-Klip, replaced Nick Chopper's limbs with tin prosthetics until he was made entirely out of tin, but didn't give him a heart. As a result, he lost his ability to love altogether and never married Nimmie Amee.
Pretty similar to losing someone to drugs, really. Little by little the human parts are replaced with something cold and mechanical, until the need and want for the drugs renders them almost (if not entirely) incapable of being able to love.
It gets even more fucked up when Nimmie marries a guy the tinsmith created out of Nick Chopper's body parts (with a different guy's head) named Chopfyt. I don't know why the tinsmith couldn't have just put Nick Chopper back together in the first place, I guess that wouldn't be weird enough.