The present invention relates to a composition, a laminate, a packaging material, a battery case packaging material, and a battery, and the composition includes: a modified olefin polymer (A) that is a modified olefin polymer, the modified olefin polymer being a polymer (a) of a C2 to C20 α-olefin modified by a monomer (b) having a functional group reactive with an epoxy group or an oxazoline group; a crosslinking agent (B) including at least one of an epoxy compound and an oxazoline compound; and a catalyst (C) having a pKa of 11 or more, the modified olefin polymer (A) satisfying the following requirements (i) and (ii): Requirement (i): the polymer (a) contains a structural unit derived from a C4 to C20 α-olefin, and Requirement (ii): a heat of fusion of the polymer (A), as measured according to JIS K7122, is 0 to 50 J/g.