I'm not familiar with the band Metallica. Are you a fan?
They are actually my favorite band.  The were created in 1981 by Lars Ulrich and James Hetfield
What are some of their songs?
There most well known song is Enter Sandman.  It led to their album selling over 30 million copies
Wow! That is quite an accomplishment. How were they received critically? Did they receive any awards?
They have won several awards since their inception.  Their most recent album Death Magnetic also was critically praised
Are they still performing today?
Metallica
Metallica is an American heavy metal band. The band was formed in 1981 in Los Angeles, California, by drummer Lars Ulrich and vocalist/guitarist James Hetfield, and has been based in San Francisco, California for most of its career. The group's fast tempos, instrumentals and aggressive musicianship made them one of the founding "big four" bands of thrash metal, alongside Megadeth, Anthrax and Slayer. Metallica's current lineup comprises founding members Hetfield and Ulrich, longtime lead guitarist Kirk Hammett and bassist Robert Trujillo
Enter Sandman
"Enter Sandman" is a song by American heavy metal band Metallica. It was released as the first single from their self-titled fifth album, "Metallica" in 1991. The music was written by Kirk Hammett, James Hetfield and Lars Ulrich. Vocalist and rhythm guitarist Hetfield wrote the lyrics, which deal with the concept of a child's nightmares.
The single achieved platinum certification for more than 1,000,000 copies shipped in the United States, spurring sales of over 30 million copies for "Metallica