Learn Spanish (Latin America): El maíz congelado está en la lata.

It is acting as an adjective meaning 'frozen', but it comes from a verb! Congelado is the past participle of the regular -ar verb congelar (to freeze). To form it, you just drop the -ar and add -ado.

Would the ending of congelado change if we were talking about mixed vegetables instead of corn?

Yes! When you use a past participle like an adjective, it has to match the noun in gender and number. Because el maíz is masculine and singular, it is congelado. For a feminine plural noun like las verduras (the vegetables), it would become congeladas.

Why do we use está instead of es in this sentence?

We use está (from the verb estar) because the sentence tells us where the corn is located right now (in the can). In Spanish, you always use estar to talk about physical location.

Why does maíz have an accent mark on the 'i'?

The accent mark tells you how to pronounce the word. It breaks the 'a' and 'i' into two separate syllables with the stress on the 'i' (mah-EES). Without the accent mark, those vowels would blend together into a single syllable.