The day before, Trump had called for Russian Federation to be reinstated to the group, despite its annexation of Ukraine's Crimea region four years ago, a stance that broke with the other leaders at the gathering.
Many social media users began to share Merkel's, suggesting there's noticeable tension in the photo.
He then tore into Canadian prime minister Justin Trudeau in a pair of tweets, calling him "very dishonest and weak" and attacking his "false statements" after Mr Trudeau reasserted his strong opposition to the United States tariffs in a news conference.
Trump said Saturday that he has a great relationship with his allies. Despite this, they were seen at the summit on good terms, and President Macron's team said his talks with Trump were "frank and robust".
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Kathleen Wynne's Liberals, meanwhile, were reduced to just seven seats, falling short of official party status in the legislature. In style, his campaign took a page from that of Donald Trump, emphasizing the leader over the party.
While many said that the picture sums up Trump's time at G7, several others called it a "power dynamic".
Mrs Merkel's photo has taken off on social media, spawning all sorts of memes and amusing caption contests.
Shortly afterwards, the White House issued a separate photo showing a sitting Mr Trump speaking as Mrs Merkel, Mr Abe and Canadian Prime Minister Justin Trudeau listen.
The captions reads: "Day two of the G7 summit in Canada: spontaneous meeting between two working sessions".
Soon afterwards, Trump rejected in a series of angry tweets from Air Force One the text of a G7 consensus statement - traditionally a paean to shared Western values and objectives under American leadership.