The 45-year-old rapper, whose real name is Marshall Mathers, was introduced on stage by fellow Detroit rapper Big Sean and Alex Moscou, one of the survivors of the mass shooting at Marjory Stoneman Douglas High School in Parkland, Florida, last month.
Instead of singing the first verse of his single "Nowhere Fast," the artist broke into an explicit freestyle criticizing the NRA.
"This whole country is going nuts and the NRA is in our way," he rapped.
"They're responsible for this whole production/they hold strings, they control the puppet/and they threaten to take donor bucks/so they know the government won't do nothing and no one's budging/ gun owners clutching their loaded weapons/they love their guns more than our children," he went on.
The emphatic freestyle was met with enthusiasm by the live audience. However, some of the rapper's critics were quick to point to Eminem's gun-related incidents, including one in 2000 when he was charged with possession of a concealed weapon and assault and another gun-related transgression a year later for which he received a sentence of probation and community service.
"When I [put out ‘The Storm'], I felt that everybody who was with him at that point doesn't like my music anyway," Eminem told Billboard in January. "I get the comparison with the non-political-correctness, but other than that, we're polar opposites."
"I know that Hillary [Clinton] had her flaws, but you know what? Anything would have been better [than Trump]. A f***ing turd would have been better as a president," he added.
In an interview with New York Magazine published online in December, the Detroit rapper said the president "makes my blood boil."
"I can't even watch the news anymore because it makes me too stressed out," he said.