It is not necessarily a bad thing. If a person has a really bad cold or influenza, or some other kind of infection, a fever is a way that the body can burn up the poisons (ie the infection) and any toxins which are in the system.
Intense sweating is a sign that the unwanted matter is being purged from the system, so treatment is not always required. If a fever is supprssed then the toxins cannot be expelled.
However, it is very important to take lots of fluids to help replenish lost fluids and ensure that the organs in the body have enough fluid to 'wash out' the system. If a fever is very high or lasts for two or three days then medical advice should always be sought.