Maalik is an angel mentioned in the Islamic scriptures. He is the one who is in charge or keeper of Hell.
One must believe that the angels are from the creation of Allah; no one knows their exact number except Him. They are from the unseen world. Allah created them to worship and obey Him. They carry out all of Allah’s orders, from administration, observation, guarding and protecting the universe as well its creatures, all according to Allah’s Will and Order.
And they will cry: "O Maalik (Keeper of Hell)! Let your Lord make an end of us." He will say: "Verily you shall abide forever." (Quran Surah43:77)
Allah has charged the angels with specific duties, and they do what they are commanded. Allah says: "They fear their Lord above them, and they do what they are commanded." (Quran Surah16:50)
The angels are not partners, associates, or rivals with Allah, nor are they His children; but one must still respect and love them. Allah says: "And they say: ‘The Most Beneficent (Allah) has begotten a child [from the angels].’ Far removed is He from every imperfection! They (the angels) are but honored slaves. They speak not until He has spoken, and [then] they act on His Command." (Quran Surah21:26-27)
They spend their time worshipping and obeying Allah, glorifying Him and praising Him. Allah says: "They (i.e. the angels) glorify His praises night and day, (and) without slackening (to do so)." (Quran Surah21:20)
The angels were created from light. The Prophetﷺsaid: 'The angels were created from light, the Jinn were created from a smokeless flame of fire, and Adam was created from what was described to you (black dry clay).' Sahih Muslim 2996 
And Prophet Muhammad (May Allah honor Him and grant Him Peace) was shown Maalik, the keeper of Hell, and the Dajjal (one-eyed, Non-believer), with the signs that Allah revealed to him on this night. Sahih Al Bukhari Vol 4:462 andSahih Al Muslim Vol 1: 316.
A Muslim must believe specifically in all the angels named and/or described in the Qur'an and the ahadith: