Due to stability issues, carbyne, a one-dimensional chain of carbon atoms, has been much less investigated than other recent carbon allotropes such as graphene. Beyond that, metalation of such a linear carbon nanostructure with regularly distributed metal atoms is even more challenging. Here, through an on-surface synthesis approach, we report a successful on-surface synthesis of metalated carbyne chains by dehydrogenative coupling of ethyne molecules and copper atoms on a Cu(110) surface under ultrahigh vacuum conditions. The length of the fabricated metalated carbyne chains is found to extend into the submicron scale (with the longest ones up to ~120 nm). We expect that the herein developed on-surface synthesis strategy towards the efficient synthesis of organometallic carbon-based nanostructures will inspire more extensive experimental investigations on their physicochemical properties and explorations of their potential with respect to technological applications.