Is there mention of Maitreya Buddha in Pali Canon? How did this idea of next Buddha formed? Is it the influence of other religion where they say Kalki or Christ will return. 

Also does Pali Canon mention many other Buddha before Gautam Buddha?
How did this idea of next Buddha formed? Is it the influence of other religion where they say Kalki or Christ will return.


No need for outside influence, just simple logic. It doesn't make any sense to have only one single Gautama Buddha arisen in a universe (or multiverse) with unfathomably long history without descernable beginning and end.


  Also does Pali Canon mention many other Buddha before Gautam Buddha?


Yes, see the Buddhavamsa, the 14th Book of the Pali Canon's Khuddaka Nikaya for the list of 24 Buddhas predecessors to Gautama Buddha. See DN 26 for infos. on Metteyya, the future Buddha.