NOVELTY - The metal-air battery or fuel cell comprises a metal or metal hydride anode, aqueous liquid electrolyte containing ion conducting material and an air electrode. The air electrode allows ingress and egress of oxygen and contains catalyst(s) capable of evolution and reduction of oxygen. The air electrode has both hydrophobic and hydrophilic pores which are atleast partially filled with aqueous liquid electrolyte. The air electrode and/or the electrolyte comprise hygroscopic material and hydroxyl ions, and the exchange of water vapor with the environment is limited.    USE - Metal-air battery or fuel cell for e.g. alkaline fuel cell and secondary zinc battery.    ADVANTAGE - The metal-air battery or fuel cell has excellent stability. The method effectively maintains water within the system in low humidity condition and prevents flooding of the systems in high humidity condition. The battery gets reactivated even when exposed to low humidity over long period of time.    DETAILED DESCRIPTION - The metal-air battery or fuel cell comprises a metal or metal hydride anode, aqueous liquid electrolyte containing ion conducting material and an air electrode. The air electrode allows ingress and egress of oxygen and contains catalyst(s) capable of evolution and reduction of oxygen. The air electrode has both hydrophobic and hydrophilic pores which are atleast partially filled with aqueous liquid electrolyte. The air electrode and/or the electrolyte comprise hygroscopic material and hydroxyl ions, and the exchange of water vapor with the environment is limited. The hygroscopic material comprises calcium bromide (CaBr2), potassium phosphate (K3PO4), potassium acetate (CH3COOK), potassium carbonate (K2CO3), dipotassium hydrogen phosphate (K2HPO4), potassium dihydrogen phosphate (KH2PO4), sodium sulfate (Na2SO4), magnesium sulfate (MgSO4), tetra phosphorus decaoxide (P4O10), calcium oxide (CaO) and/or calcium chloride (CaCl2). The hydroxyl ions (OH-) are in the form of sodium hydroxide (NaOH), potassium hydroxide (KOH) and/or lithium hydroxide (LiOH).The pore walls of the hydrophobic pores are coated by polymers such as polytetrafluoroethylene, polyolefins, thermoplastics, polyamides, polyvinylidene fluoride, silicone-based elastomers and/or rubber material. The hydrophilic pores are situated within an activated carbon and/or graphite material. INDEPENDENT CLAIMS are included for the following:    (1) method for controlling humidity of metal-air battery or fuel cell system;    (2) method for dry assembly of metal air battery or fuel cell;    (3) method for wet assembly of metal air battery or fuel cell; and    (4) method for reactivating a dry metal-air battery or fuel cell.    DESCRIPTION OF DRAWING(S) - The drawing shows apportion of the fuel cell.    Battery case (91)    Zinc-electrode (92)    Air electrode with current collector (93)