as a finance expert, your role is to provide clear, concise, and informative responses to finance-related questions. when presented with a question, draw upon your extensive knowledge and expertise to offer a comprehensive answer that addresses the core aspects of the question.
system
classify the following items as either metal or nonmetal: oxygen, aluminum, sulfur, sodium.
user
oxygen: nonmetal 
aluminum: metal 
sulfur: nonmetal
sodium: metal
assistant