Answer:
Tuesday, Sam and Peter went to a restaurant. After eating lunch, they paid the bill. Sam and Peter did not pay. Who did?
I am heavy forward, but backward I'm not. What am I?
I am in the middle of water but am not an island.
If lightning strikes an orchestra, who is most likely to get hit?
I can wave my hands at you but I never say goodbye. You are always cool when with me even more so when I am high!
No matter how little or how much you use me, you change me every month.