When Eminem raps, people listen.

And boy, were they listening Tuesday night.

The Detroit rapper unleashed on President Donald Trump in a taped freestyle rap that aired during the BET Hip Hop Awards.

While Eminem -- who apparently filmed the rap last Friday in a downtown Detroit parking garage -- has been vocal against Trump in the past, he took it to a different level this time, raising a fist and "drawing a line in the sand" against any of his fans who support Trump.

(WARNING: Video contains explicit language -- app users watch here)

He also raised his fist for Colin Kaepernick, the NFL quarterback who began the protests against racial injustice and police brutality during the national anthem last year and has been a target of criticism from Trump and others for what they call "disrespecting the flag."

Kaepernick was among those who took notice on Twitter, telling Eminem: "I appreciate you."

Cleveland Cavaliers star LeBron James also chimed in with his favorite lyric from the rap.

Overall, Eminem has been trending nationally on Facebook and Twitter. Here are some of the top reactions:

Best political writing of the year, period. πŸ‘πŸ‘πŸ‘πŸ‘πŸ‘#Eminem2020 https://t.co/yS2Y72n8WS

— Keith Olbermann (@KeithOlbermann) October 11, 2017

Trump himself hasn't tweeted about Eminem's rap (yet), but did tweet that he's glad NFL commissioner Roger Goodell is "demanding that all players STAND for our great National Anthem."