There are a number of factors that influence stocks each week, but the first few days of a new month are particularly important given two critical reports about auto sales and unemployment.

Early in the week, stocks are likely to be influenced by news out of the nation's largest car and truck manufacturers, as they begin rolling out sales figures for the month of May.

The big question is whether they'll be able to continue their momentum from last month. In April, General Motors (NYSE:GM) reported a nearly 7% increase in vehicle sales despite the still-tepid economy. And Fiat Chrysler notched a 14% gain thanks to a strong performance from its Jeep branded sport-utility vehicles and Ram pickup trucks.

The one carmaker left in the dust in April was Ford (NYSE:F). Sales at the company fell, albeit by less than 1%, over the month. As my colleague Daniel Miller discussed at the time, the drop was the result of a dismal performance by Ford's Lincoln brand and lackluster demand for the American automaker's car segment.

With GDP statistics recently suggesting the economy contracted in the first-quarter of the year, analysts and investors will be watching the updated figures from the month of May closely.

The second big report this week, due out on Friday, concerns the government's official estimate of unemployment. While the unemployment rate has dropped considerably since the peak of the Great Recession, it's since gained additional momentum.

In April, employers added jobs at one of the fastest rates during the recovery. Nonfarm payrolls, the principal metric used by economists to gauge the health of the labor market, expanded by 288,000 during the month. Additionally, the unemployment rate dropped to 6.3%, or the lowest level in six years.

Of course, this metric alone arguably overstates the health of the American worker, as large swaths of otherwise employable workers have stopped looking for work and thereby dropped out of the labor force (and thus the denominator of the unemployment rate). Additionally, the length of unemployment remains at a historic high.

Given this, analysts and investors will be watching the official report closely for signs that last month's momentum was part of a larger trend and not merely an outlier.