Outgoing German Chancellor, Angela Merkel, is among the dignitaries who are in the Italian capital for the two-day gathering. Among the topics being discussed is the coronavirus pandemic - with emergency workers invited to join the leaders for a photo. Tackling global warming is also top of the agenda, ahead of the COP26 climate conference which begins on Sunday. Most of those attending the G20 in Rome will travel onward to Glasgow for that key UN climate summit.
It is Biden's first major European trip to meet world leaders as president. The devout Catholic keeps a photograph of Pope Francis on his desk at the White House. He met with his hero face-to-face at the Vatican.
For more than an hour, the two leaders spoke privately about climate change, the pandemic and poverty. The visit is the prequel of two major summits happening this weekend. In Rome, the G20 and in Glasgow the COP26 climate summit. Back home, Biden suffered a setback for his pricy infrastructure plan, which focuses in part on the environment.
But ahead of the G20, young people are pushing for action on the climate.
Getting more jabs in people's arms in rich and poor countries is also a priority at the first face-to-face summit since the pandemic hit. But before Biden joins in on the global cooperation to tackle monumental problems, he first had a very public Mea Culpa with French President Emmanuel Macron.
Biden apologized for the US's botched handling of a submarine deal with Australia, which cut out France. For his part Macron is ready to move forward. Both sides hope the rebuilding of trust will help bring about the change young people are marching for.
