鉄
てつ · tetsu · JLPT N3 · noun
iron
🔩 鉄 = 金 metal + 失 lose: the metal that loses itself to rust
The left side 金 marks metals. The right side 失 means lose, and iron is the metal that rust eats away. Fun fact: before the post-war reform the kanji was 鐵. The 失 version started as a shortcut, so treat this as a memory hook, not true etymology.