Seal Sings on Ellen -- 'LET'S STAY TOGETHER'

Seal may or may not have a message for Heidi Klum -- singing Al Green's "Let's Stay Together" on today's episode of "Ellen."

Barack Obama performed his own rendition of the famous break-up song just days ago -- but given the timing of Seal's split from Heidi ... we doubt his performance was an homage to POTUS.

Among the lyrics -- "Baby, let's, let's stay together / Loving you whether, whether times are good or bad, happy or sad."

The song appears on Seal's new album -- but there are plenty of other songs he could have chosen to perform.

So we gotta ask ...