This study investigates the role of metacognition in the consumer persuasion process, specifically examining the role of thought confidence in the formation of attitudes and attitude confidence among consumers exposed to advertisements. The study consists of three studies. Study 1 examines the self-validation effect of model attractiveness in the brand attitude formation process of consumers exposed to advertising. Study 2 investigates the influence of personality variables on thought confidence and the relationship between thought confidence and attitude confidence. Study 3 examines the effect of thought source on the likelihood of thought-related word-of-mouth and the mediating role of thought confidence. For all three studies, experimental advertisements were presented to participants, and data were collected through questionnaires. The results showed that thought confidence was higher when elaboration likelihood was higher, and the thought confidence generated by advertising model attractiveness was greater when elaboration likelihood was high and imagistic impressions were weak (vs. otherwise). Furthermore, this confidence was found to play a moderating role in the influence of message arguments (central cues) on brand attitude formation. However, when elaboration was low, consumers did not undergo the self-validation process, and model attractiveness directly influenced brand attitude merely as a peripheral cue (Study 1). Additionally, personality variables influenced thought confidence: thought confidence was higher when need for cognition was high, private self-consciousness was high, and self-monitoring was low. Moreover, thought confidence was found to have a positive effect on attitude confidence (Study 2). It was also confirmed that when individuals generated thoughts on their own without being exposed to others' arguments, they had higher thought confidence than otherwise. Furthermore, higher thought confidence was associated with a greater likelihood of communicating one's thoughts to others through word-of-mouth, and thought confidence was confirmed to play a mediating role in this process (Study 3).