Honda and Nissan said on Monday that they are starting merger talks.Josh Lefkowitz via Getty ImagesHonda's shares soared by as much as 17% when local markets opened on Tuesday.The automaker said on Monday that it was starting merger discussions with struggling rival Nissan.Honda also announced a $7 billion stock buyback program.Honda's shares soared after the company said it was in talks to merge with rival automaker Nissan.Honda's stock went up as much as 17% when local markets opened on Tuesday, a day after it announced that it had begun discussions with Nissan.