I also had them give me a topic to create similes and metaphors for as a class before they did some as small groups. Our topic - Minecraft! Little did I know it is becoming a little less popular for some 4th graders, but they still came up with fun similes and metaphors!
Core Connection: 4th grade English Language Arts, Language Standard 5 a. Explain the meaning of simple similes and metaphors (e.g. pretty as a picture) in context.