There is more than one artist with this name.

Samhain was a deathrock/horror punk band formed by Glenn Danzig in 1983 as The Misfits were in major turmoil and close to disbanding. Danzig originally planned Samhain as a side project, but after the demise of The Misfits in October of 1983, it became his full-time band. Samhain is the lesser known of Glenn Danzig's musical outlets, and catalogs the transitional period of his musical career, bridging the gap between the punk thrashing of The Misfits, and the dark, heavy metal sound of Danzig.

Glenn took the name of the band from Samhain, the ancient Celtic New Year, which influenced the modern Halloween. Samhain is pronounced "sow-win" (which is the pronunciation that Glenn uses in songs), although the band name is often pronounced "Sam-Hane" for the sake of simplicity.

Samhain was much darker than The Misfits, with lyrics rooted in the horrors of reality and the occult, as opposed to the sometimes cartoonish ghouls and ghosts of The Misfits. Samhain's musical style was a dark, gritty, and experimental combination of punk, gothic rock, and on the last album, heavy metal.

Samhain released two full-length albums and one EP during their three year career as an active band. Some criticized their first album for being merely the Misfits slowed down, but Samhain demonstrated noticeably superior musicianship. The fact that Samhain re-recorded a few Misfits songs cemented the idea in some peoples' minds that Danzig couldn't move past his work with the Misfits. However, as their career progressed, they evolved into their own unique style of lo-fi goth metal and gained a cult following that surpassed the modest fan base The Misfits had while they were active.

As a footnote, Glenn wrote the songs Bloodfeast and Death Comes Ripping with intentions of using them on the first Samhain album, but they ended up on Earth A.D./Wolfs Blood album as part of a last ditch effort to salvage the band.

It is also the name of a danish Black/Death metal band, who later changed name to Desexult. They only released one demo under the name Samhain, called "The Courier", released in 1985.

It is also the name of a Celtic folk band.

One more band under this name is a Slovakian industrial act, started in 1997, but managed to release their first full-length album "Violent Identity" only in 2006 at Aliens Productions. Their style can be described as a successful mix of old-school dark electro and idm with a touch of industrial sound.

German Thrash Metal band Deathrow were initially called Samhain. They released three demos under that name before renaming to Deathrow:
-The Lord of the Dead (1985)
-Eternal Death (1986)
-Live (1986)

And one more band under this name is a Russian satanic black metal band from Naberezhnye Chelny. Main members - "Death" and "Carcass". "Carcass" made his own project Izgoi
Official Site