Explain why your finger sticks to a metal ice tray just taken from your refrigerator.

Heat is transferred between a system and its environment when their temperature differs. Energy is transferred by thermal conduction. Metal is good conductor of heat. When you touch the metal ice tray, heat will transfer from your finger to the bit of ice and the ice melts results a thin film of water between the finger and the metal tray. Again the water film will freeze because the metal tray is so cold. Thus an icy bond will create in between the metal tray and your finger. That is why your finger sticks to a metal ice tray just taken from your refrigerator.