This chapter considers AI not only as a technological tool but also as a socio-technical system. AI literacy is defined as a complex concept, posing challenges for its integration into STEM education. The chapter specifically focuses on secondary education and addresses two research questions: (1) How do STEM teachers understand AI literacy and perceive the use of AI in their daily teaching practices? (2) How can we support STEM teachers in enhancing their professional competencies to foster students’ AI literacy development? Grounded in a theoretical framework linking AI literacy, STEM education, and teacher education, empirical work is conducted with mathematics teachers to explore their perceptions of AI use in Danish high schools through qualitative interviews. The results inform the development of various strategies for professional development that support both STEM teachers and students in advancing AI literacy in secondary education.