Is this a simile or metaphor The Sun with all those planets revolving around it and dependent on it can still ripen a bunch of grapes as if it had nothing else in the world to do?

Answer 1

It is more accurately a simile, but it is a metaphor also (all similes are metaphors, but not all metaphors are similes). Break it down...

The Sun - the subject

...with all those planets revolving around it and dependent on it - subordinate prep phrase

...can still ripen - the predicate, verb phrase

...a bunch of grapes - object

...as if it had nothing else in the world to do - prepositional phrase, and here's the metaphor. The comparison made is between the sun and a living being who has a conscious choice of activities.

Similes use like or as to make the comparison, think of either of these two words as the pivot point on a seesaw. In this case, The Sun... is on one side of the seesaw;...it had nothing else to do is on the other side; ...as...sits in the middle and balances the two.

Similes are explicit parallels, that is the comparison between the unlike things is drawn by the use of like and as(sometimes than).

Metaphors are implied parallels, that is the comparison between the unlike things is directly expressed.

If the sentence had been worded: The Sun has nothing else in the world to do but ripen a bunch of grapes, this would still be a metaphor but not a simile.