About 6,000 policemen will be deployed in the capital for her 6-hour visit, turning the city centre into a no-go zone for protest marches planned by labour unions and opposition parties.
"We don't want her here," said Yannis Georgiou, 72, who has seen his pension cut by one third. "We will take to the streets against austerity and against the government. Maybe Merkel will hear something and see what we're going through."
Merkel's visit is a sign of Germany's support for the coalition government of Prime Minister Antonis Samaras as it struggles to agree new budget cuts with international lenders, overcome the objections of reluctant coalition partners and cope with rising public anger.
After toying with the idea of a Greek exit from the euro zone in the first half of 2012, Merkel has come full circle and decided the risks of the country leaving are too high, especially with a German election looming next year.
The trip is a sign of German solidarity, a message to the Greek leadership and people that Berlin does not want to cut them loose, and a signal to the members of Merkel's coalition who want Greece out that it's not going to happen soon.