Theresa May will make her first visit to Wales as the new prime minister where she will meet with First Minister Carwyn Jones in Cardiff.
The pair are expected to discuss the fallout of June's Brexit vote.
The future of the Tata Steel plant in Port Talbot, where more than 4,000 jobs are at risk, is also on the agenda.
Mr Jones previously admitted he knows "very little" about Mrs May but hopes she would be able to deliver an improved devolution settlement.
Speaking ahead of the visit, she said: "In my first statement as prime minister I made clear how strongly I believe in the union.
'Vital' steel industry
"I want to say to the people of Wales that the government I lead will always be on your side - and that means I will stand up for you and your family against injustice and inequality.
"My government is committed to helping the steel industry secure a long-term viable future in Wales.
"The steel industry is vital to the UK and we will do everything we can to look after the workers and wider community as we work with Tata and the Welsh Government.
"Whether it's reforming the economy or strengthening our society, we are going to build a better Britain and a nation that works for everyone - not just the privileged few."
Mrs May succeeded David Cameron as prime minister last Wednesday, and vowed to lead a "one nation" government.
On Friday, she visited Scotland's First Minister Nicola Sturgeon where she described the meeting in Edinburgh as "positive".