The metal parts on top of a gas range where you place your frying pan or pots are called "burner grates" or "burner grills." These grates are designed to support your cookware and allow the flames from the gas burners to heat the bottom of the pans evenly. Burner grates are typically made of cast iron, enamel-coated cast iron, or stainless steel, depending on the model and brand of the gas range.
The design and size of the burner grates can vary depending on the specific gas range model, but their main function is to provide a stable and safe platform for cooking utensils while ensuring proper heat distribution during the cooking process. They are an essential part of a gas range and play a crucial role in achieving consistent and efficient cooking results.