Chinese President Xi Jinping has arrived in the UK at the start of a four-day state visit which UK PM David Cameron has said hails a "golden era" in ties between the two countries.
Mr Cameron's spokesman has said "nothing is off the table" when it comes to talks between the pair.
Earlier, the prime minister told MPs he would raise the issue of subsidised Chinese steel with his counterpart.
Human rights and cyber attacks are also likely to be discussed.
The visit comes after Chancellor George Osborne visited China last month, where he said it was the government's intention to make the UK China's "best partner in the west".
Mr Osborne also announced earlier this month that the UK will allow Chinese companies to take a stake in British nuclear power plants - a move questioned by some.
Mr Cameron told Chinese state TV Mr Xi's visit marks a "very important moment".
The Communist leader and his wife Peng Liyuan arrived at Heathrow Airport, where they were greeted on behalf of the Queen by Viscount Hood. Foreign Secretary Philip Hammond joined the welcome party.
Large red flags of the People's Republic of China are lining The Mall in central London, along with the union jack, in preparation for the official welcome on Horse Guards Parade on Tuesday.
During their visit they will meet members of the Royal Family and stay at Buckingham Palace, visit businesses and address members of the Houses of Parliament at Westminster.
Amnesty International and other groups concerned with human rights issues in China are expected to protest in St James' Park on Tuesday and it is expected that there will also be a pro-China protest.
The start of the visit comes as parts of Caparo steel were put into administration - with unions saying cheap steel from abroad may be a cause.
Concerns have already been raised about the impact of cheap steel from China on the European market. Shadow business secretary Angela Eagle said earlier that "anti-competitive dumping... is driving down steel prices."
Mr Cameron told the Commons: "We're doing everything we can in Europe to help our steel industry.
"That is why we voted in favour of dumping tariffs against the Chinese and we'll do everything we can to help our steel industry, including looking at how we help on high energy usage and the clearances that we need with that.
"Will we raise it with the Chinese? Of course, we'll raise all these issues. That is what our relationship with China is all about."
Who is China's President Xi?
- Born in Beijing in 1953
- Son of Xi Zhongxun, a revolutionary who helped to found the People's Republic of China
- Father purged in 1962, Xi sent to work in a remote village aged 15
- Joined Communist Party in 1974
- Became party chief of Shanghai in 2007
- Communist Party leader since 2012
- Pro-business, anti-corruption
- Married to actress and singer Peng Liyuan since 1987
Mr Cameron's spokeswoman also said she expected human rights and the threat faced from cyber attacks to come up during talks.
Developing a strong and engaged relationship "means we are able to talk to them... frankly and with mutual respect," she added.
China's ambassador to the UK, Liu Xiaoming, said on Sunday that his country does not "shy away" from discussing human rights.
Mr Liu said he doubted Labour leader Jeremy Corbyn would raise human rights abuses during a state banquet at Buckingham Palace this week after Mr Corbyn's spokesman said he would use the visit to discuss the issue.
Meanwhile, the Duke of Cambridge has recorded a speech on the illegal ivory trade for Chinese state TV.
He also raised the issue with Mr Xi when they met in Beijing earlier this year and his broadcast will form part of a series of programmes called Let's Talk.
Also ahead of Mr Xi's visit, former defence secretary Liam Fox questioned the deal with China over nuclear power.
Dr Fox said he would be happier if "central elements" of software were produced in the UK.
Asked if he was happy with the arrangement, Dr Fox said: "I think we have to question it."
China state visit: The timetable
- President Xi and his wife Peng Liyuan receive a ceremonial welcome at Horse Guards Parade before travelling in a carriage procession along The Mall to Buckingham Palace
- Later, Mr Xi will address members of the Houses of Parliament
- The president is due to meet Labour leader Jeremy Corbyn
- The Queen will give a state banquet at Buckingham Palace
- Mr Xi will visit Imperial College London with the Duke of York and Chancellor George Osborne
- He will meet David Cameron at Downing Street before before visiting the UK-China Business Summit at Mansion House and then Chinese telecommunications company Huawei Technologies
- Mr Xi, joined by the Duke of York, will visit Inmarsat, a global satellite communication services company, before attending a Confucius Institute conference hosted by UCL Institute of Education
- In the evening, Mr Xi and Ms Peng will join Mr and Mrs Cameron at Chequers for dinner before flying to Manchester
- Mr Xi will visit the National Graphene Institute at the University of Manchester with Mr Osborne and then the City Football Group with Mr Cameron
- The president and Mr Cameron will attend an event at Manchester Airport before Mr Xi and Ms Peng depart