The Icelandic side, who qualified as Group Three winners, raced into a 6-0 half-time lead after goals from Svava Gudmundsdottir (2), Rakel Hönnudottir (2), Fanndis Fridriksdottir and Berglind Thorvaldsdottir.
Malfridur Sigurdardottir and Esther Arnarsdottir both scored late on.
Met finished third behind runners-up Spartak Subotica, who beat them 3-2.
The Welsh side began their campaign with a 4-0 win over NSA Sofia.
Cardiff Met missed out on place in the Uefa Women's Champions League knock-out stages after defeat by Breidablik.