what does modal verb mean?
A modal verb is a type of verb that is used to indicate modality – that is: likelihood, ability, permission and obligation. Examples include the English verbs can/could, may/might, must, will/would and shall/should. In English and other Germanic languages, modal verbs are often distinguished as a class based on certain grammatical properties.
Spanish, like French, uses fully conjugated verbs followed by infinitives. For example, poder "to be able" (Puedo andar, "I can walk"), deber "to have an obligation" (Debo andar, "I should walk"), and querer "to want" (Quiero andar "I want to walk").
The correct use of andar in these examples would be reflexive. "Puedo andar" means "I can walk", "Puedo irme" means "I can go" or "I can take myself off/away". The same applies to the other examples.