This thesis discusses the use of cognitive linguistics, more precisely the conceptual metaphor theory (CMT) and metaphorical awareness, in the teaching of idiomatic expressions in Slovene and English as foreign languages. When it comes to foreign language learning the importance of being familiar with and comprehending idiomatic expressions in the target language is particularly considerable. Idiomatic expressions can serve as the windows into the foreign language culture and society while also representing an important and pervasive feature of everyday communication in a FL. We demonstrate that metaphor is central to language and language use and that foreign language learners need to engage with it to develop language proficiency. We explore how learners might usefully engage with them, in order to understand, learn and use idioms in FL and present some sample CMT-based learning materials and guidelines on idiomatic expressions.