If you have lead attributes that you want to carry over to contact, account, or opportunity attributes after conversion, you can set up lead mapping rules.
For an example, let's say we have a Competitor attribute on a lead that we want to carry over to an attribute on the opportunity after conversion.
First, let's make sure we have the corresponding attribute on opportunities. To verify, go to your opportunities and then click the Gear menu and then Configure Attributes.
Here you can see that we have the Competitor attribute already created on opportunities.
Now go to your leads and click on the Gear menu and then Configure Attributes
And then find the Competitor attribute, hover over the Pencil menu, and then click Edit
You'll see the Converts To settings here
Choose the object type and attribute you want to map to
When you're done, click Modify and then close the dialog.
To show you how this works in action, let's take this lead with the Competitor attribute set set to 'Acme' and click Convert
After filling out the opportunity data, click the Convert button
And on the newly created opportunity, we have the Competitor attribute set to 'Acme'.