A machine learning engineer is responsible for developing and deploying machine learning models and systems. They collaborate with data scientists and software engineers to collect, preprocess, and analyze data, ensuring the models are accurate and efficient. Machine learning engineers often work on tasks such as algorithm development, model training, and optimization, using programming languages like Python and tools such as TensorFlow or PyTorch. They also integrate machine learning solutions into existing systems and ensure scalability and reliability for real-world applications.