Gay and women's rights groups have criticised Eminem heavily, although gay singer Sir Elton John, who will duet with Eminem at the Los Angeles ceremony, has defended the rapper.
Long established superstars like Madonna and U2 will be there as well as newcomers Macy Gray and Dido, but they are being largely ignored while the record industry debates the merits of the multi-Grammy nominated 28-year-old.
Gay and women's rights groups have criticised Eminem heavily, although gay singer Sir Elton John, who will duet with Eminem at the Los Angeles ceremony, has defended the rapper.
Police numbers for the ceremony are being doubled because of planned protests.
Many music industry figures, including Madonna and Stevie Wonder, have been supportive of Sir Elton.
"Well, I think it has to be allowed," said veteran crooner Tony Bennett at a pre-Grammy party.
"We live in a free country. If it were to be censored we'd be in a Nazi country."
Insult
But singer Gladys Knight was shocked that her "pal", Elton John, would do anything with Eminem.
"I need the details," said Knight, "I have to talk to Elton. I have to call my buddy and say 'What is going on?'"
Lynne Cheney, wife of US vice-president Dick Cheney, has also joined the attack.
She told CNN: "Elton John has been so good in the past speaking out on issues of equality for gay people, on issues of being against violent language against gay people.
"I am quite amazed and dismayed that he would choose to perform with Eminem."
She added: "This is a man who talks about murdering his own mother, he talks about murdering women generally.
"He talks about killing them slowly so you can hear them scream for a long time."
Gay activists complain that Eminem's Grammy-nominated album, The Marshall Mathers LP, which has sold 10 million copies worldwide, contains 18 uses of the word "faggot".
Eminem, whose real name is Marshall Mathers III, has four Grammy nominations, including album of the year, best rap album, and best rap solo performance.
He is also nominated for best rap performance and best rap performance by a duo or group for the track Forget About Dre on Dr Dre's album Dr Dre - 2001.
Fans say his album is "visionary", and rants about gays and women are not meant to be taken seriously.
"To me his lyrics are funny. I think they are misunderstood, people are over-analysing them, " said Andrea Aguilar, a Los Angeles high school student who runs an Eminem web site.
Eminem himself has said his lyrics should be taken with a "grain of salt".
Also in the running
U2 and Madonna will also perform at Wednesday's ceremony.
Both acts, who have won multiple Grammys in the past, are in the running for more titles this year.
U2, who have won seven Grammys, are competing against Madonna in the record of the year category with their single Beautiful Day.
The track - a number one hit in 32 countries - is in the race for song of the year, which credits song writing talent.
Madonna has won five Grammys in the past, mostly for her 1998 album Ray of Light.
Her nominations this year include record of the year for Music, the title track from her current album.
But overall, the awards - as well as the ceremony - are expected to be dominated by Eminem and his mentor Dr Dre, who has five nominations.