In the present tense, the verb "to be" is almost always omitted.

"I am a student" = «я студент»
"I am old" = «я стар/стара» (depending if the speaker is male or female)
"It is stupid" = «оно глупо»
"The box is small" = «коробка — мала» (note that here a dash is used to in place of "is", you do not need to use this with pronouns such as «я», «ты», «вы», «он» etc.)

However, for "I am sixteen [years]", a completely different structure is used - «мне шестнадцать [лет]». Literally, this means "to me sixteen [years]".

Similarly, for "my name is Jimmy", you wouldn't say «моё имя — Джимми», you say «меня зовут Джимми» - literally "me they call Jimmy".