Depends on which missionaries in what era.
Christian
Christianity :)
Spanish missionaries, or the priests who ran Spanish missions in the Americas, taught the Spanish language and the customs of catholicism to the natives of the American continents. The missionaries provided education in the areas of language and reading as well as religion to the natives. They also claimed to provide spiritual guidance in the catholic fashion for the purpose of redeeming the souls of the natives. The missionaries spread important aspects of the Spanish culture, such as language and religion, into the native culture of the Americas.
Roman Catholicism was introduced to Mexico by Spanish missionaries. To such degree, that nowadays, it is by far its largest faith (88%).
Roman Catholicism, particularly though the use of Jesuit missionaries.
religion
The country is a majority of Catholic. It was settled by the Spanish who always had Catholic missionaries with them.
Guatemalas main recognized religion is catholic brought over from the Spanish. However there are many indigenous Indians that practice there own religion and spanish both. Also many missionaries have brought evangelist type worship.
Spain exiled Moors in Spain before 1492. Spain also sent missionaries to Spain to Christianize the natives.
Actually, the Spanish missionaries who came to the Andean nations were predominantly Catholic rather than Baptist. They played a significant role in the conversion of the local populations to Catholicism, which became the predominant religion in the region due to the influence of Spanish colonization.
This question is far too vague. Missionaries for which religion? What location is being asked about.
They brought new religious ideas