1. Onto indicates movement from one position to another one.

Pattern 1: verb + onto + noun
The child hopped onto the bed.

Typical verbs used before onto:
drip, fall, hop, jump, move, run, spill, step

Pattern 2: verb + noun + onto + noun
We moved all the books onto the desk.

Typical verbs used with this pattern:
drip, drop, move, spill, transfer

2. Onto indicates knowledge of misbehavior.

Pattern: be + onto + noun.
The police are onto that gang about the missing money.

Fact
In July 1874, a swarm of Rocky Mountain locusts flew over Nebraska covering an area estimated at 198,600 square miles. It is estimated that the swarm contained about 12.5 trillion insects. These insects became extinct thirty years later      .. More >>