Which of the following welding types is characterized by the joining of two overlapping pieces of metal?

A fillet weld is indeed characterized by the joining of two overlapping pieces of metal. It is used to create a weld joint at right angles and is commonly used to connect parts at corners, such as the edges of structural members. The shape of a fillet weld resembles a triangular cross-section and is applied to the joints where two parts meet, allowing for a strong bond between them. This type of weld is versatile and can be used in various applications, including structural steel components and other metalworking projects.

Groove welds, on the other hand, are used for joining parts that are aligned edge-to-edge and typically involve creating a groove that is filled with weld metal. A plug weld is utilized to join two overlapping metals but requires a hole in one of the pieces through which molten metal is deposited. Arc welding refers to the welding process itself rather than a specific type of weld joint. Thus, the fillet weld stands out as the correct choice for the described scenario of overlapping pieces of metal.