The invention provides a composition for chemical-mechanical polishing. The composition comprises an abrasive, a first metal rate polishing modifier agent, a second metal rate polishing modifier agent, and a liquid carrier. In one embodiment, the first metal rate polishing modifier agent has a standard reduction potential less than 0.34 V relative to a standard hydrogen electrode, and the second metal rate polishing modifier agent has a standard reduction potential greater than 0.34 V relative to a standard hydrogen electrode. In other embodiments, the first and second metal rate polishing modifier agents are different oxidizing agents.