In this chapter, I will argue that the idea of Conceptual Metaphor Theory (CMT) can help us to deepen our understanding of the link between the form and meaning of language, and contribute to effective language teaching. Our focus is on the issue of spatio-temporal metaphors, which are linguistic representations in which meanings about time are metaphorically described by languages about space. First, I will look at the basic spatio-temporal metaphors of English and Japanese to see how our conceptualization of time consists of metaphorical uses of concepts about space. I will then turn to the peculiar Japanese space-to-time mappings. We will find that while similar ideas can be found in the English and Japanese spatio-temporal metaphors, there are also cultural differences between the two. The discussion in this chapter will suggest that the view of CMT can help learners to effectively understand the systematic network of meanings of language and to deepen their understanding of the characteristics of various languages in terms of the modes of conceptualization behind them.