Some embodiments include methods of forming metal-containing structures. A first metal-containing material may be formed over a substrate. After the first metal-containing material is formed, and while the substrate is within a reaction chamber, hydrogen-containing reactant may be used to form a hydrogen-containing layer over the first metal-containing material. The hydrogen-containing reactant may be, for example, formic acid and/or formaldehyde. Any unreacted hydrogen-containing reactant may be purged from within the reaction chamber, and then metal-containing precursor may be flowed into the reaction chamber. The hydrogen-containing layer may be used during conversion of the metal-containing precursor into a second metal-containing material that forms directly against the first metal-containing material. Some embodiments include methods of forming germanium-containing structures, such as, for example, methods of forming phase change materials containing germanium, antimony and tellurium.