To Broil Fish you must first understand how to broil.

 

Broiling (exclusive to American and Canadian English) or grilling (elsewhere in the English speaking world) is a process of cooking food with high heat with the heat applied directly to the food, most commonly from above. Heat transfer to the food is primarily via thermal radiation. As it is a way of cooking without added oil, it is popular in low-fat diets.
In electric ovens, broiling/grilling may be accomplished by placing the food near the upper heating element, with the lower heating element off and the oven door partially open. Gas ovens often have a separate compartment for broiling, as a drawer below the flame.
Similar to a broiler/grill is a salamander, which is most frequently used in a professional kitchen. It is smaller than a standard broiler/grill, and is used to finish off dishes, such as caramelizing the sugar on a Crème brûlée.
The terminology merits a further note: broiling is known as grilling in British English and Australian English, but grilling in American English refers to cooking done over an open flame on a grid-iron, not to be confused with barbecue or cooking over low indirect heat. During the 1990's 'grilling' also became used in the USA for double-sided frying with something like a commercial electric grill. Popular US promoters of electric double-sided frying appliance have opted for the 'global' term 'grilling' rather than the geographicaly isolated term broiler.
In 1898 Bridge & Beach Co., St. Louis, MO. started manufacturing a vertical cast iron stove. These stoves were designed so that the meat could be flame broiled from both sides at the same time. Hinged steel wire gridirons were designed for use in the vertical broilers. The hinged gridirons were slid in & out of the stoves holding the meat while it cooked evenly on both sides.
Cooking meat at high temperatures, such as broiling/grilling or barbecuing, can lead to the formation of heterocyclic amines, which are carcinogens.