Yes, is is present tense. It is the third-person singular form of to be, used with he, she, or it, and its past-tense partner is was.
So The kettle is hot means hot right now, while The kettle was hot puts it in the past.
How it looks in sentences
The bus is late again. Spoken this morning, that one word pins the delay to right now, not yesterday, and it works because a bus is a singular it.
Was covers the same idea after the fact, as in The bus was late again. The present version, The bus is late again, works because is pairs with just one person or thing being talked about, a third-person singular subject. Add more buses and the verb changes: in The buses are late, the plural subject takes are, not is.
'Was' is not the only past form
Was is the past-tense form of is, so they name the same idea at different times: The kettle is hot now, The kettle was hot earlier. One boundary to note: be has other past forms besides was, so was is the past form of is specifically, not of every form of the verb.