In multimodal human-robot interaction (HRI), the process of communication can be established through verbal, non-verbal, and/or para-verbal cues. The linguistic literature shows that para-verbal and non-verbal communications are naturally synchronized, however the natural mechnisam of this synchronization is still largely unexplored. This research focuses on the relation between non-verbal and para-verbal communication by mapping prosody cues to the corresponding metaphoric arm gestures. Our approach for synthesizing arm gestures uses the coupled hidden Markov models (CHMM), which could be seen as a collection of HMM characterizing the segmented prosodic characteristics' stream and the segmented rotation characteristics' streams of the two arms articulations. Experimental results with Nao robot are reported.