Monitoring MySQL performance is crucial to ensure the smooth operation of your database. Key metrics to monitor include query throughput, slow queries, connection utilization, and buffer pool usage. Query throughput metrics such as Questions, Com_select, and Queries provide insight into the number of queries executed, while slow queries can indicate potential bottlenecks. Connection metrics like Threads_connected, Threads_running, Connection_errors_max_connections, and Aborted_connects help identify issues with client connections. Buffer pool metrics like Innodb_buffer_pool_pages_total, Buffer pool utilization, Innodb_buffer_pool_read_requests, and Innodb_buffer_pool_reads are essential for understanding storage engine performance. By monitoring these key metrics, you can gain real-time insight into your database's health and performance, identify potential constraints, and take corrective action to optimize MySQL performance.