The British Prime Minister told leaders free trade and globalisation has to work for everyone as she told them Britain is a multicultural country which is open to trade.
She also spoke about slavery as the “scourge of our world” as she urged leaders to take responsibility for cutting it out and look after those who are being "left behind".
Mrs May hit out at far-right and far-left parties are using people's anger and fears to create immediate solutions which will not last in the world of today.
The Tory leader said the British people have fixed their eyes on a brighter future to "build a truly global Britain" as she said she knows much of the rest of the world, especially "our friends" in Europe, do not understand why the UK is leaving the EU.
Theresa May was speaking at the Davos World Economic Forum
In a speech tailored to those elite leaders in Davos, Switzerland, Mrs May said: "Those of us who meet here are all optimists who believe in the power of public and private cooperation to make the world of tomorrow better than today.
"We are all united in our belief that that world will be built on the foundation of free trade, partnership and globalisation.
"Yet beyond the confines of this hall those forces for good we take for granted are being called in to question the forces of liberalisation and free trade that have an overwhelming impact on our world, the forces that underpin the rules based international system which is key to our global beliefs of unity are at risk of being undermined.
"Across Europe parties of the far left and right are seeking to exploit this opportunity gathering support by feeding off an underlying sense felt by some people with modest to low incomes living in relatively rich countries in the west are not working for them.
"Those parties who embrace the politics of division and despair, who offer solutions which are easy, feed off the sense in the public that mainstream and political leaders have failed to address their problems."
Addressing Britain’s decision to leave the EU, she said the UK, “as a truly global Britain” is a country that reaches beyond Europe’s borders too.
Mrs May said leaders need to make getting rid of slavery a priority
She told the forum: "We are going to be a confident country that is in control of its own destiny once again.
"We will forge a new place in the world. The road may be uncertain at times but those who voted for Brexit believe in a brighter future for Britain and that's why we are on a bold ambitious course. They chose a truly global Britain.
"Let us not underestimate the magnitude of that decision. Britain must face up to a period of momentous change, it means we must go through a tough negotiation and forge a new role for ourselves in the world, it means accepting that the road ahead will be uncertain at times."
She welcomed preliminary trade talks which are underway with several countries including Australia, New Zealand and India and revealed China and the Gulf States have expressed interest in making deals with Britain.
Giving an example of how global Britain is, she said Jaguar Land Rover, which are "quintessentially British", are owned by India's Tata.
Speaking to global leaders, she said Britain was open to the world
This was Mrs May's first time in the alpine resort speaking as Britain's Prime Minister and came two days after she spoke in London to lay out a 12-point Brexit plan.
A source earlier this morning said the message "won't be combative" but said: "The PM is reflecting themes she's spoken about before – that change has to come in order to benefit who have been left behind."
As Home Secretary Mrs May introduced the Modern Slavery Act to Britain two years ago.
Theresa May's 12 point Brexit plan
Mon, January 16, 2017
It's finally here!
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Continued cooperation with the EU to tackle terrorism and international crime.
The Davos summit has already proved eventful, with US Vice President Joe Biden yesterday accusing Russian president Vladimir Putin of using "corruption" to destroy the Western, liberal world order.
He also urged against “Islamaphobia” and “building walls”.
Mr Biden said Russia is trying to use underhand tactics to expose faultlines in the EU and slowly erode it until it crumbles.
The 74-year-old said the nationalist wave sweeping across the world, as evidenced by Brexit, Trump's election and Marine le Pen's meteoric rise in France, was a potentially "dangerous" thing.
Mr Biden said: "Some people are trying to capitalise on this anti-Islamic spirit. They think the answer is to build walls and shut the gates.
"But that's precisely the wrong answer. It doesn't resolve the causes of those problems.
"Illiberal actors will equate their success with ruining the international order."