So welcome to the monster legends breeding chart. Here are the following combos you should go after to breed the monsters you are looking for.
Fire Monsters
Firesaur + Metalsaur = Esmelter or Fornax
Firesaur + Genie = Pyrook or Djinn
Firesaur + Tyranno King = Flickie or Firetaur
Firesaur + Mersnake= Sealion or Vapwhirl
Firesaur + Thunder Eagle = Gigram or Thundernix
Firesaur + Rockilla = Firekong or Freetle
Firesaur + Treezard = Greenasaur or Pandaken
Nature Monsters
Treezard + Metalsaur = Jonskeer or Crux
Treezard + Light Spirit = Vixsun or Rudicius
Treezard + Genie = Bloomskips or Pandalf
Treezard + Tyrannoking = Sealion or Vapwhirl
Treezard + Mersnake = Sheluke or Bumblesnout
Treezard + Rockilla = Rarawr or Tarzape
Treezard + Firesaur = Greenasaur or Pandaken
Earth Monsters
Rockilla + Metalsaur = Rockneto or Gravoid
Rockilla + Light Spirit = Light Sphinx or Goldcore
Rockilla + Tyrannoking = Obsidia or Beefcake
Rockilla + Mersnake = Gastosquish or Musu
Rockilla + Thunder Eagle = Electrex or Bonbon
Rockilla + Treezard = Rarawr or Tarzape
Rockilla + Firesaur = Firekong or Freetle
Water Monsters
Mersnake + Metalsaur = Metanephrops or Metaslach
Mersnake + Light Spirit = Bleestle or Raane
Mersnake + Genie = Dolphchamp or Octocrush
Mersnake + Thunder Eagle = Shock Turtle or Koopigg
Mersnake + Rockilla = Gastosquish or Musu
Mersnake + Treezard = Sheluke or Bumblesnout
Mersnake + Firesaur = Sealion or Vapwhirl
Electric Monsters
Thunder Eagle + Metalsaur = Lesaki or Garuda M3
Thunder Eagle + Light Spirit = Pelitwirl or Pulseprism
Thunder Eagle + Genie = Raydex or Sparkwedge
Thunder Eagle + Tyrannoking = Terror Dactyl or Shanky
Thunder Eagle + Mersnake = Shock Turtle or Koopigg
Thunder Eagle + Rockilla = Electrex or Bonbon
Thunder Eagle + Firesaur = Gigram or Thundernix
Dark Monsters
Tyrannoking + Metalsaur = Omethyst or Vortux
Tyrannoking + Light Spirit = Succuba or Fayemelina
Tyrannoking + Genie = Giragast or Haze
Tyrannoking + Thunder Eagle = Terror Dactyl or Shanky
Tyrannoking + Rockilla = Obsidia or Beefcake
Tyrannoking + Treezard = Utochomp or Dendrosaur
Tyrannoking + Firesaur = Flickie or Minotaurus
Magic Monsters
Genie + Metalsaur = Manolyth or Dommeath
Genie + Light Spirit = Flawless or Zim
Genie + Tyrannoking = Giragast or Haze
Genie + Mersnake = Dolphchamp or Octocrush
Genie + Thunder Eagle = Raydex or Sparkwedge
Genie + Treezard = Bloomskips or Pandalf
Genie + Firesaur = Pyrook or Djinn
Light Monsters
Light Spirit + Metalsaur = Heimdal or Aurinia
Light Spirit + Genie = Flawless or Zim
Light Spirit+ Tyrannoking = Succuba or Fayemelina
Light Spirit + Mersnake = Blesstle or Raane
Light Spirit + Thunder Eagle = Pelitwirl or Pulseprism
Light Spirit + Rockilla = Light Sphinx or Goldcore
Light Spirit + Treezard = Vixsun or Rudicius
Metal Monsters
Metalsaur + Light Spirit = Heimdal or Aurinia
Metalsaur + Genie = Manolyth or Dommeath
Metalsaur + Tyrannoking = Omethyst or Vortux
Metalsaur + Mersnake = Methanephrops or Metaselach
Metalsaur + Thunder Eagle = Lesaki or Garuda M3
Metalsaur + Treezard = Jonskeer or Crux
Metalsaur + Firesaur = Esmelter or Fornax
Epic Monsters
Pyrook + Treezard = Erpham
Bloomskips + Firekong = Tartarus
Tyrannoking + Beefcake = Darknubis
Mersnake + Genie = Drop Elemental
Electrex + Koopigg = Musu
Electrex + Vixsun = Goldcore
Pyrook + Utochomp = Pandalf
Utochomp + Light Sphinx = Fayemelina
Light Sphinx + Pyrook = Skipples or Duchess
Utochomp + Koopigg = Razfeesh or Rhynex
Electrex + Pandaken = Rabidex
Bonbon + Pandaken = Rhynex
Legendary Monsters
Fayemelina + Darknubis = Darkzgul
Erpham + Drop Elemental = Goldfield
Rabidex + Tartarus = Thorder
Rhynex + Darknubis = Nemestrinus
Razfeesh + Drop Elemental = Lord of Atlantis
Skipples + Duchess = Vadamagma