To provide an ink composition capable of forming a metallic material which is excellent in adhesion to a substrate and free from ion migration. An ink composition having fine metallic copper particles and/or fine copper hydride particles, and fine silver oxide particles or fine metallic silver particles, dispersed in a water-insoluble organic liquid, which composition has a solid content concentration of from 10 to 80 mass % and contains from 5 to 90 parts by mass of the fine metallic copper particles and/or fine copper hydride particles, and from 10 to 95 parts by mass of the fine silver oxide particles or fine metallic silver particles, per 100 parts by mass of the total solid content in the ink composition.