A Greek exit from the euro zone would have such a large impact on Germany's economy that German policymakers would make all efforts to never let it happen, said Dennis Gartman of "The Gartman Letter."

The election of left-wing Prime Minister Alexis Tsipras has renewed chatter about the possibility of a Greek exit from the euro zone, as the country struggles to pay back billions of dollars in loans.

On CNBC's "Fast Money" on Monday, Gartman explained how Germany's economy would be rocked if Greece were to leave.

"Germany can't let Greece go," he said. "Germany is an export country. It needs to have a euro that is basically weak on balance. It knows that if it let Greece go, the euro would skyrocket."

Gartman's take centered around the fact that Germany relies on exports to drive its economy. If Greece were to leave the euro zone, he said, the euro would climb and therefor make German exports more expensive in other countries.

"Germany needs a weak country such as Greece, and other weak countries such as Spain and Portugal to keep pressure upon the euro, to keep the euro going lower so that their export businesses will continue to thrive."

Gartman said people may be surprised by the performance of European stocks in the coming months if the euro continues to weaken.

"I think European stocks can outperform U.S. stocks for the next several months. I think people will be surprised by that fact."

—By CNBC's Michael Newberg