A metal foam ball, several millimeters in diameter, is manufactured to have an open-pore structure to absorb fluid (e.g., gas and liquid) such as water or lubricant. As an example, a copper foam ball is manufactured via a freeze casting method using prepared oxide powder slurry where a spherical silica gel mold is used to freeze the slurry, which is subsequently dried at low temperature in vacuum and then sintered at high temperature. For improved oxidation, copper alloy foam ball or copper foam ball coated with tin can also be manufactured through the same method. For improved strength, steel, copper-nickel alloy, or titanium foam ball can also be manufactured through the same method.