A wellhead assembly includes a wellhead housing having a bore with a wellhead housing sidewall and a longitudinal axis. A hanger lands in the bore, the hanger having a hanger sidewall. Parallel circumferentially extending hanger sidewall ridges are located on the hanger sidewall. Each of the hanger sidewall ridges have upper and lower flanks that converge to a crest. Hanger sidewall bands are located between adjacent ones of the hanger sidewall ridges. A metal seal ring has an outer seal surface in metal-to-metal sealing engagement with the wellhead housing sidewall and an inner seal surface in metal-to-metal sealing engagement with the hanger sidewall bands. Crests of the hanger sidewall ridges embed into the inner seal surface to restrict relative movement between the hanger and the seal ring. A recess extends through each of the hanger sidewall ridges from the upper flank to the lower flank to allow any fluid trapped between the hanger sidewall ridges to flow out.