Precisely at the percolation threshold, we show that a superconductor-insulator composite in 2d behaves like a normal metal, with a conductance g e which is a universal function of the material parameters. For a composite of BCS superconductor and insulator, we find that g ̃ e = C( g ̃ D g ̃ n ε I ) 1 2 , where ε I is the dielectric constant of the insulating component, g ̃ D = Δd/e 2 , Δ is the BCS energy gap, d is the film thickness, and C is a dimensionless constant of order unity. g̃ e and g̃ n are the conductances of the film at threshold, and of the normal component, both measured in units of e 2/ ħ. Very near the threshold, g̃ e falls to zero below a gap which vanishes at p c according to the power law | p − p c| s + t)/2 , where s and t are the standard percolation exponents. Above but not below p c, the composite exhibits a perfect-conductance delta-function whose strength falls to zero as ( p − p c) t .