  As the wide adoption of intelligent chatbot in human daily life, user demands
for such systems evolve from basic task-solving conversations to more casual
and friend-like communication. To meet the user needs and build emotional bond
with users, it is essential for social chatbots to incorporate more human-like
and advanced linguistic features. In this paper, we investigate the usage of a
commonly used rhetorical device by human -- metaphor for social chatbot. Our
work first designs a metaphor generation framework, which generates topic-aware
and novel figurative sentences. By embedding the framework into a chatbot
system, we then enables the chatbot to communicate with users using figurative
language. Human annotators validate the novelty and properness of the generated
metaphors. More importantly, we evaluate the effects of employing metaphors in
human-chatbot conversations. Experiments indicate that our system effectively
arouses user interests in communicating with our chatbot, resulting in
significantly longer human-chatbot conversations.
