In language teaching, assistive technologies have been used throughout history, and the integration of current technologies into language teaching has been the subject of research. Generative artificial intelligence, one of today's technologies, has had a disruptive impact in education as in many other fields, offering various opportunities for language teaching, posing threats, and prompting discussions on ethical issues. Generative artificial intelligence has provided many opportunities in language teaching, from personalization to high-quality feedback, and from the autonomy it offers to skill development. All these opportunities have also introduced threats; they have caused the roles in educational environments to be questioned and have led to discussions about the simplification of language, bias, and the digital divide. Furthermore, ethical issues concerning data privacy, copyright, and content production remain prominent, raising concerns that failure to take precautions could lead to even greater problems in the future. This chapter has comprehensively discussed all these issues, aiming to raise awareness about the use of generative AI.