Wet tongues at body temperature stick to frozen metal surfaces because the metal literally draws the heat out of the tongue.  When heat is drawn out of the tongue, saliva becomes frozen and sticks to the metal surface like superglue.  In addition, textured taste buds on your tongue strongly grip the metal surface.  Due to the intensity with which the tongue sticks to the frozen metal, pulling lightly on the tongue to remove it will not work. Pulling really hard on the tongue will only end up leaving a portion of the tongue stuck to the metal and the person bleeding profusely. If you come across someone who has managed to stick his tongue to a cold metal surface, tell him to try to remain calm and not to pull on his tongue as it will only cause damage. Unless you witnessed the person sticking her tongue to the metal surface, you may not know what happened.  Check her to make sure she's otherwise okay and not injured in other ways. If she has been hurt or injured in other ways, and those injuries are not minor (e.g. bumps or bruises) you should call 911 immediately. If you can warm up the metal, the tongue may naturally become unstuck.  On way to attempt this is to ask the person to breathe on the metal as much as possible, while cupping his hands around his mouth to direct the hot air.  You can even try to shelter the metal surface to help warm it up and contribute to the hot air being blown onto the surface. Be careful that the stuck person doesn’t also stick his lips or hands to the metal surface, as this will just make the situation worse. If you live nearby, or have access to a hot water tap, get a glass or bottle filled with warm (not hot) water.  Pour that warm water onto the person’s tongue where it’s stuck to the metal.  At this point you can tell the person to slowly pull away from the metal surface to detach her tongue.  If you are not able to get warm water, and hot air hasn’t worked, you may have to call 911 for help. The liquid doesn’t necessarily have to be water.  If you, or someone else passing...

===
Write a summary of the previous text in Vietnamese:
Động viên người đó giữ bình tĩnh và không kéo lưỡi ra. Cần biết chắc chắn là người đó không bị tổn thương gì khác. Bảo người đó hít thở sâu. Tìm chút nước ấm. Gọi cấp cứu.