Here's the structural formula for methylcyclobutane:

1. The Cyclobutane Ring:

* Draw a square. This represents the four-carbon ring of cyclobutane.

2. The Methyl Group:

* Attach a CH₃ group (methyl group) to one of the carbon atoms in the square.

3. Hydrogen Atoms:

* Add hydrogen atoms (H) to each carbon atom in the ring and the methyl group so that each carbon has four bonds.

Here's a visual representation:

```

H

|

H - C - C - H

| |

C - C - H

|

H

```

Let me know if you'd like to see a condensed structural formula or a line-angle formula for methylcyclobutane!