Gas-metal arc welding (GMAW) is a widely used fusion joining process in industry known for its ability to create high-quality welds. However, the complex and nonlinear nature of GMAW process variables often leads to weld defects in certain situations. Various dynamic factors affect the GMAW process, including power source dynamics, metal transfer dynamics, arc and droplet dynamics, and weld pool dynamics, making precise control challenging. While achieving completely defect-free welds can be difficult, some welds may still meet industry standards for acceptable performance in specific applications. Properly controlling process parameters plays a crucial role in reducing defects and enhancing overall weld quality. Advanced sensor technologies have emerged as valuable tools for monitoring and adjusting process parameters to achieve desired weld characteristics. This chapter provides a review of research on how GMAW process parameters influence the welding of carbon steels, emphasizing the importance of process control and the role of sensor technologies in improving weld quality.