Stock futures are rallying

Stock futures are rallying on Wednesday morning.

Near 7:57 a.m. ET, Dow futures were up 136 points, S&P 500 futures were up 14 points, and Nasdaq futures were up 33 points.

On Tuesday, stocks closed modestly higher, and the S&P 500 managed to turn positive again for the year after it went red in Monday's big selloff.

The big news is, of course, still Greece. The latest is that prime minister Alexis Tsipras has written a letter showing that the country is willing to accept almost all of its creditors' demands.

Shortly after midnight in Athens, the International Monetary Fund confirmed that Greece had missed its €1.6 billion ($1.8 billion) payment that was due June 30, "joining the historical ranks of delinquents from Cuba to Zimbabwe," as Credit Suisse put it in a morning note. The country's bailout program also expired.

A referendum on whether Greece will accept creditors' conditions is still scheduled for Sunday, and citizens are already leaning towards a "no" vote that could mean Greece leaves the euro, according to Reuters.

US economic data is plenty today. Private payrolls grew by 237,000 (218,000 expected,) the highest since December 2014, according to ADP.

The initial reading of US Markit Manufacturing PMI will cross at 9:15 a.m., followed by ISM Manufacturing at 10:00.

US auto sales data is rolling in throughout the day.

We got a $28.3 billion insurance mega merger to start the morning: Ace Limited is acquiring Chubb. Chubb shareholders receive $62.93 per share in cash and 0.6019 in Ace shares.