The Dow Jones Industrials (DJINDICES:^DJI) continued their run of recent success Monday, closing up 40 points as investors largely treaded water on a day that was essentially a pause in the first-quarter earnings season. But tomorrow, earnings will play a much more important role for the index, as Dow components McDonald's (NYSE:MCD) and Travelers (NYSE:TRV) report their earnings before the market opens. With much at stake in their respective industries, these two stocks could move the Dow and the entire stock market with their results.

If last quarter's releases offer any indication on timing, Travelers will issue its earnings release at about 7 a.m. EDT and McDonald's will release its report at around 8 a.m. EDT. Travelers has scheduled a 9 a.m. EDT conference call to discuss its results, while the McDonald's conference call is due to begin at 11 a.m. EDT.

McDonald's desperately needs to reestablish its ability to grow in the U.S. and worldwide, with sales releases for the first two months of the quarter raising big questions about the sustainability of the company's growth strategy. In particular, while January showed an expected divergence between weak U.S. same-store sales and stronger international comps, February showed declines in some key markets, including a 2.6% drop in the Asia-Pacific region. Competition in the U.S. has ramped up considerably in recent months, as key players in fast-food and fast-casual dining seek to erode the advantages that McDonald's has developed over its long history. To defend its turf, McDonald's must emphasize value while also attracting a different customer base to bolster its overall revenue.

Source: Travelers.

On the other hand, times couldn't be better for insurance giant Travelers, which is benefiting from a lull in large-scale catastrophic losses. The concern for shareholders, though, is that Travelers might not have anywhere to go but down from here, as an inevitable loss event will eventually cause earnings to fall, at least temporarily. For its part, Travelers is trying to move into more lucrative business lines, making sure it spends its efforts on insurance niches that are most likely to maximize profits. Yet as the insurance business cycle runs its course, a lack of losses is leading toward premium-pricing erosion, and continuance of that trend could decrease profits even without a catastrophic event.

Both McDonald's and Travelers will give investors useful information about the state of the economy within the U.S. and abroad. In particular, if McDonald's doesn't see emerging-market growth pick up markedly, it could represent yet another headwind for those economies that might suggest slowing long-term growth.