Speaking at the European Council summit, the German Chancellor sent a message of support to the Prime Minister over Brexit and rising tensions between the UK and Russia.
Leaders from EU member states have travelled to Brussels where they are expected to adopt a negotiating mandate for the future trading relationship with Britain and sign off on a two-year transition.
The German Chancellor also spoke out after facing criticism for sending a letter to the Russian President after his re-election, in the wake of the Salisbury nerve agent attack. Mrs Merkel did originally send her support to Mrs May after the UK accused Russia of the attack.
Speaking to journalists Mrs Merkel said: “We will, of course, also talk about Great Britain exiting and hopefully make some progress tomorrow when talking about the future relationship between EU and Great Britain and also pass the corresponding guidelines.
“I believe that Michel Barnier and Jean-Claude Juncker have done excellent work here.
“Of course, we will also address the terrible incident in Salisbury.
“And I have already expressed our solidarity to Theresa May and our support.
“It is good that Great Britain has also handed the substances, the chemical weapons to the chemical weapons authorities where things can be investigated.”
Leaders are due to meet on Friday to give the green light to progress made in negotiations, while Russia is also set to dominate discussions.
The President of the European Commission faced criticism after he sent a letter to President Putin too following his election victory.
Speaking to journalists in Brussels, Mrs May said: “I will also, of course, be talking about Brexit. I’m looking forward to talking about Brexit.
“We’ve made considerable progress through the agreement of the implementation period.
“I look forward to the European Council endorsing that agreement and moving on swiftly to talking about the future partnership that we all want to build together.
On Russia, Mrs May branded the attack “brazen and reckless” as she accused the Kremlin of attempted murder. She said the nerve agent attack showed “Russian aggression against European neighbours”.