97 Yukon won't start

My yukon wouldn't start this morning. I turn the ignition key and all I get is a clicking sound. Battery seems fine. Lights illuminate in and out of car. Please help.

My yukon wouldn't start this morning. I turn the ignition key and all I get is a clicking sound. Battery seems fine. Lights illuminate in and out of car. Please help.

........Just got a jump from my sister and the freaking Yukon started. Hopefully it's just the battery.

I'd really keep those terminals clean and the wires tightened in the future. I've had that happen to me in the past here in FL where batteries need to be replace once every 2 years.