Microelectronic packages having chambers and sealing materials, and methods of making the packages, and sealing the chambers, are disclosed. An exemplary package may include a first surface, a second surface, a solid sealing material including an intermetallic compound, such as, for example, of gallium or another relatively low melting material, between the first surface and the second surface, and a chamber defined by the first surface, the second surface, and the sealing material. An exemplary method may include disposing a ring of a sealing material including a liquid metal between a first surface and a second surface to define a chamber between the first surface, the second surface, and the ring of the sealing material, and sealing the chamber by heating the sealing material to react the liquid metal with a metal that is capable of forming an intermetallic compound with the liquid metal.